Java 反编译工具的使用与对比分析

前言

Java 反编译，一听可能觉得高深莫测，其实反编译并不是什么特别高级的操作，Java 对于 Class 字节码文件的生成有着严格的要求，如果你非常熟悉 Java 虚拟机规范，了解 Class 字节码文件中一些字节的作用，那么理解反编译的原理并不是什么问题。甚至像下面这样的 Class 文件你都能看懂一二。

一般在逆向研究和代码分析中，反编译用到的比较多。不过在日常开发中，有时候只是简单的看一下所用依赖类的反编译，也是十分重要的。

恰好最近工作中也需要用到 Java 反编译，所以这篇文章介绍目前常见的的几种 Java 反编译工具的使用，在文章的最后也会通过编译速度、语法支持以及代码可读性三个维度，对它们进行测试，分析几款工具的优缺点。

Procyon

Github 链接：https://github.com/mstrobel/procyon Procyon 不仅仅是反编译工具，它其实是专注于 Java 代码的生成和分析的一整套的 Java 元编程工具。主要包括下面几个部分：

Core Framework
Reflection Framework
Expressions Framework
Compiler Toolset (Experimental)
Java Decompiler (Experimental)

可以看到反编译只是 Procyon 的其中一个模块，Procyon 原来托管于 bitbucket，后来迁移到了 GitHub，根据 GitHub 的提交记录来看，也有将近两年没有更新了。不过也有依赖 Procyon 的其他的开源反编译工具如** decompiler-procyon**，更新频率还是很高的，下面也会选择这个工具进行反编译测试。

使用 Procyon

<!-- https://mvnrepository.com/artifact/org.jboss.windup.decompiler/decompiler-procyon -->
<dependency>
    <groupId>org.jboss.windup.decompiler</groupId>
    <artifactId>decompiler-procyon</artifactId>
    <version>5.1.4.Final</version>
</dependency>

写一个简单的反编译测试。

package com.wdbyte.decompiler;

import java.io.IOException;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Iterator;
import java.util.List;

import org.jboss.windup.decompiler.api.DecompilationFailure;
import org.jboss.windup.decompiler.api.DecompilationListener;
import org.jboss.windup.decompiler.api.DecompilationResult;
import org.jboss.windup.decompiler.api.Decompiler;
import org.jboss.windup.decompiler.procyon.ProcyonDecompiler;

/**
 * Procyon 反编译测试
 *
 *  @author https://github.com/niumoo
 * @date 2021/05/15
 */
public class ProcyonTest {
    public static void main(String[] args) throws IOException {
        Long time = procyon("decompiler.jar", "procyon_output_jar");
        System.out.println(String.format("decompiler time: %dms", time));
    }
    public static Long procyon(String source,String targetPath) throws IOException {
        long start = System.currentTimeMillis();
        Path outDir = Paths.get(targetPath);
        Path archive = Paths.get(source);
        Decompiler dec = new ProcyonDecompiler();
        DecompilationResult res = dec.decompileArchive(archive, outDir, new DecompilationListener() {
            public void decompilationProcessComplete() {
                System.out.println("decompilationProcessComplete");
            }
            public void decompilationFailed(List<String> inputPath, String message) {
                System.out.println("decompilationFailed");
            }
            public void fileDecompiled(List<String> inputPath, String outputPath) {
            }
            public boolean isCancelled() {
                return false;
            }
        });

        if (!res.getFailures().isEmpty()) {
            StringBuilder sb = new StringBuilder();
            sb.append("Failed decompilation of " + res.getFailures().size() + " classes: ");
            Iterator failureIterator = res.getFailures().iterator();
            while (failureIterator.hasNext()) {
                DecompilationFailure dex = (DecompilationFailure)failureIterator.next();
                sb.append(System.lineSeparator() + "    ").append(dex.getMessage());
            }
            System.out.println(sb.toString());
        }
        System.out.println("Compilation results: " + res.getDecompiledFiles().size() + " succeeded, " + res.getFailures().size() + " failed.");
        dec.close();
        Long end = System.currentTimeMillis();
        return end - start;
    }
}

Procyon 在反编译时会实时输出反编译文件数量的进度情况，最后还会统计反编译成功和失败的 Class 文件数量。

....
五月 15, 2021 10:58:28 下午 org.jboss.windup.decompiler.procyon.ProcyonDecompiler$3 call
信息: Decompiling 650 / 783
五月 15, 2021 10:58:30 下午 org.jboss.windup.decompiler.procyon.ProcyonDecompiler$3 call
信息: Decompiling 700 / 783
五月 15, 2021 10:58:37 下午 org.jboss.windup.decompiler.procyon.ProcyonDecompiler$3 call
信息: Decompiling 750 / 783
decompilationProcessComplete
Compilation results: 783 succeeded, 0 failed.
decompiler time: 40599ms

Procyon GUI

对于 Procyon 反编译来说，在 GitHub 上也有基于此实现的开源 GUI 界面，感兴趣的可以下载尝试。 Github 地址：https://github.com/deathmarine/Luyten

CFR

GitHub 地址：https://github.com/leibnitz27/cfr CFR 官方网站：http://www.benf.org/other/cfr/（访问可能需要FQ） Maven 仓库： https://mvnrepository.com/artifact/org.benf/cfr

CFR（Class File Reader）可以支持 Java 9、Java 12、Java 14 以及其他的最新版 Java 代码的反编译工作。而且 CFR 本身的代码是由 Java 6 编写，所以基本可以使用 CFR 在任何版本的 Java 程序中。值得一提的是，使用 CFR 甚至可以将使用其他语言编写的的 JVM 类文件反编译回 Java 文件。

CFR 命令行使用

使用 CFR 反编译时，你可以下载已经发布的 JAR 包，进行命令行反编译，也可以使用 Maven 引入的方式，在代码中使用。下面先说命令行运行的方式。

直接在 GitHub Tags 下载已发布的最新版 JAR. 可以直接运行查看帮助。

# 查看帮助
java -jar cfr-0.151.jar --help

如果只是反编译某个 class.

# 反编译 class 文件，结果输出到控制台
java -jar cfr-0.151.jar WindupClasspathTypeLoader.class
# 反编译 class 文件，结果输出到 out 文件夹
java -jar cfr-0.151.jar WindupClasspathTypeLoader.class --outputpath ./out

反编译某个 JAR.

# 反编译 jar 文件，结果输出到 output_jar 文件夹
➜  Desktop java -jar cfr-0.151.jar decompiler.jar --outputdir ./output_jar
Processing decompiler.jar (use silent to silence)
Processing com.strobel.assembler.metadata.ArrayTypeLoader
Processing com.strobel.assembler.metadata.ParameterDefinition
Processing com.strobel.assembler.metadata.MethodHandle
Processing com.strobel.assembler.metadata.signatures.FloatSignature
.....

反编译结果会按照 class 的包路径写入到指定文件夹中。

CFR 代码中使用

添加依赖这里不提。

<!-- https://mvnrepository.com/artifact/org.benf/cfr -->
<dependency>
    <groupId>org.benf</groupId>
    <artifactId>cfr</artifactId>
    <version>0.151</version>
</dependency>

实际上我在官方网站和 GitHub 上都没有看到具体的单元测试示例。不过没有关系，既然能在命令行运行，那么直接在 IDEA 中查看反编译后的 Main 方法入口，看下命令行是怎么执行的，就可以写出自己的单元测试了。

package com.wdbyte.decompiler;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.benf.cfr.reader.api.CfrDriver;
import org.benf.cfr.reader.util.getopt.OptionsImpl;

/**
 * CFR Test
 *
 * @author https://github.com/niumoo
 * @date 2021/05/15
 */
public class CFRTest {
    public static void main(String[] args) throws IOException {
        Long time = cfr("decompiler.jar", "./cfr_output_jar");
        System.out.println(String.format("decompiler time: %dms", time));
        // decompiler time: 11655ms
    }
    public static Long cfr(String source, String targetPath) throws IOException {
        Long start = System.currentTimeMillis();
        // source jar
        List<String> files = new ArrayList<>();
        files.add(source);
        // target dir
        HashMap<String, String> outputMap = new HashMap<>();
        outputMap.put("outputdir", targetPath);

        OptionsImpl options = new OptionsImpl(outputMap);
        CfrDriver cfrDriver = new CfrDriver.Builder().withBuiltOptions(options).build();
        cfrDriver.analyse(files);
        Long end = System.currentTimeMillis();
        return (end - start);
    }
}

JD-Core

GiHub 地址：https://github.com/java-decompiler/jd-core JD-core 官方网址：https://java-decompiler.github.io/ JD-core 是一个的独立的 Java 库，可以用于 Java 的反编译，支持从 Java 1 至 Java 12 的字节码反编译，包括 Lambda 表达式、方式引用、默认方法等。知名的 JD-GUI 和 Eclipse 无缝集成反编译引擎就是 JD-core。 JD-core 提供了一些反编译的核心功能，也提供了单独的 Class 反编译方法，但是如果你想在自己的代码中去直接反编译整个 JAR 包，还是需要一些改造的，如果是代码中有匿名函数，Lambda 等，虽然可以直接反编译，不过也需要额外考虑。

使用 JD-core

        <!-- https://mvnrepository.com/artifact/org.jd/jd-core -->
        <dependency>
            <groupId>org.jd</groupId>
            <artifactId>jd-core</artifactId>
            <version>1.1.3</version>
        </dependency>

为了可以反编译整个 JAR 包，使用的代码我做了一些简单改造，以便于最后一部分的对比测试，但是这个示例中没有考虑内部类，Lambda 等会编译出多个 Class 文件的情况，所以不能直接使用在生产中。

package com.wdbyte.decompiler;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.jar.JarFile;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.StringUtils;
import org.jd.core.v1.ClassFileToJavaSourceDecompiler;
import org.jd.core.v1.api.loader.Loader;
import org.jd.core.v1.api.printer.Printer;

/**
 * @author https://github.com/niumoo
 * @date 2021/05/15
 */
public class JDCoreTest {

    public static void main(String[] args) throws Exception {
        JDCoreDecompiler jdCoreDecompiler = new JDCoreDecompiler();
        Long time = jdCoreDecompiler.decompiler("decompiler.jar","jd_output_jar");
        System.out.println(String.format("decompiler time: %dms", time));
    }
}


class JDCoreDecompiler{

    private ClassFileToJavaSourceDecompiler decompiler = new ClassFileToJavaSourceDecompiler();
    // 存放字节码
    private HashMap<String,byte[]> classByteMap = new HashMap<>();

    /**
     * 注意：没有考虑一个 Java 类编译出多个 Class 文件的情况。
     * 
     * @param source
     * @param target
     * @return
     * @throws Exception
     */
    public Long decompiler(String source,String target) throws Exception {
        long start = System.currentTimeMillis();
        // 解压
        archive(source);
        for (String className : classByteMap.keySet()) {
            String path = StringUtils.substringBeforeLast(className, "/");
            String name = StringUtils.substringAfterLast(className, "/");
            if (StringUtils.contains(name, "$")) {
                name = StringUtils.substringAfterLast(name, "$");
            }
            name = StringUtils.replace(name, ".class", ".java");
            decompiler.decompile(loader, printer, className);
            String context = printer.toString();
            Path targetPath = Paths.get(target + "/" + path + "/" + name);
            if (!Files.exists(Paths.get(target + "/" + path))) {
                Files.createDirectories(Paths.get(target + "/" + path));
            }
            Files.deleteIfExists(targetPath);
            Files.createFile(targetPath);
            Files.write(targetPath, context.getBytes());
        }
        return System.currentTimeMillis() - start;
    }
    private void archive(String path) throws IOException {
        try (ZipFile archive = new JarFile(new File(path))) {
            Enumeration<? extends ZipEntry> entries = archive.entries();
            while (entries.hasMoreElements()) {
                ZipEntry entry = entries.nextElement();
                if (!entry.isDirectory()) {
                    String name = entry.getName();
                    if (name.endsWith(".class")) {
                        byte[] bytes = null;
                        try (InputStream stream = archive.getInputStream(entry)) {
                            bytes = IOUtils.toByteArray(stream);
                        }
                        classByteMap.put(name, bytes);
                    }
                }
            }
        }
    }

    private Loader loader = new Loader() {
        @Override
        public byte[] load(String internalName) {
            return classByteMap.get(internalName);
        }
        @Override
        public boolean canLoad(String internalName) {
            return classByteMap.containsKey(internalName);
        }
    };

    private Printer printer = new Printer() {
        protected static final String TAB = "  ";
        protected static final String NEWLINE = "\n";
        protected int indentationCount = 0;
        protected StringBuilder sb = new StringBuilder();
        @Override public String toString() {
            String toString = sb.toString();
            sb = new StringBuilder();
            return toString;
        }
        @Override public void start(int maxLineNumber, int majorVersion, int minorVersion) {}
        @Override public void end() {}
        @Override public void printText(String text) { sb.append(text); }
        @Override public void printNumericConstant(String constant) { sb.append(constant); }
        @Override public void printStringConstant(String constant, String ownerInternalName) { sb.append(constant); }
        @Override public void printKeyword(String keyword) { sb.append(keyword); }
        @Override public void printDeclaration(int type, String internalTypeName, String name, String descriptor) { sb.append(name); }
        @Override public void printReference(int type, String internalTypeName, String name, String descriptor, String ownerInternalName) { sb.append(name); }
        @Override public void indent() { this.indentationCount++; }
        @Override public void unindent() { this.indentationCount--; }
        @Override public void startLine(int lineNumber) { for (int i=0; i<indentationCount; i++) sb.append(TAB); }
        @Override public void endLine() { sb.append(NEWLINE); }
        @Override public void extraLine(int count) { while (count-- > 0) sb.append(NEWLINE); }
        @Override public void startMarker(int type) {}
        @Override public void endMarker(int type) {}
    };
}

JD-GUI

GitHub 地址：https://github.com/java-decompiler/jd-gui JD-core 也提供了官方的 GUI 界面，需要的也可以直接下载尝试。

Jadx

GitHub 地址：https://github.com/skylot/jadx Jadx 是一款可以反编译 JAR、APK、DEX、AAR、AAB、ZIP 文件的反编译工具，并且也配有 Jadx-gui 用于界面操作。 Jadx 使用 Grade 进行依赖管理，可以自行克隆仓库打包运行。

git clone https://github.com/skylot/jadx.git
cd jadx
./gradlew dist
# 查看帮助
 ./build/jadx/bin/jadx --help
 
jadx - dex to java decompiler, version: dev

usage: jadx [options] <input files> (.apk, .dex, .jar, .class, .smali, .zip, .aar, .arsc, .aab)
options:
  -d, --output-dir                    - output directory
  -ds, --output-dir-src               - output directory for sources
  -dr, --output-dir-res               - output directory for resources
  -r, --no-res                        - do not decode resources
  -s, --no-src                        - do not decompile source code
  --single-class                      - decompile a single class
  --output-format                     - can be 'java' or 'json', default: java
  -e, --export-gradle                 - save as android gradle project
  -j, --threads-count                 - processing threads count, default: 6
  --show-bad-code                     - show inconsistent code (incorrectly decompiled)
  --no-imports                        - disable use of imports, always write entire package name
  --no-debug-info                     - disable debug info
  --add-debug-lines                   - add comments with debug line numbers if available
  --no-inline-anonymous               - disable anonymous classes inline
  --no-replace-consts                 - don't replace constant value with matching constant field
  --escape-unicode                    - escape non latin characters in strings (with \u)
  --respect-bytecode-access-modifiers - don't change original access modifiers
  --deobf                             - activate deobfuscation
  --deobf-min                         - min length of name, renamed if shorter, default: 3
  --deobf-max                         - max length of name, renamed if longer, default: 64
  --deobf-cfg-file                    - deobfuscation map file, default: same dir and name as input file with '.jobf' extension
  --deobf-rewrite-cfg                 - force to save deobfuscation map
  --deobf-use-sourcename              - use source file name as class name alias
  --deobf-parse-kotlin-metadata       - parse kotlin metadata to class and package names
  --rename-flags                      - what to rename, comma-separated, 'case' for system case sensitivity, 'valid' for java identifiers, 'printable' characters, 'none' or 'all' (default)
  --fs-case-sensitive                 - treat filesystem as case sensitive, false by default
  --cfg                               - save methods control flow graph to dot file
  --raw-cfg                           - save methods control flow graph (use raw instructions)
  -f, --fallback                      - make simple dump (using goto instead of 'if', 'for', etc)
  -v, --verbose                       - verbose output (set --log-level to DEBUG)
  -q, --quiet                         - turn off output (set --log-level to QUIET)
  --log-level                         - set log level, values: QUIET, PROGRESS, ERROR, WARN, INFO, DEBUG, default: PROGRESS
  --version                           - print jadx version
  -h, --help                          - print this help
Example:
  jadx -d out classes.dex

根据 HELP 信息，如果想要反编译 decompiler.jar 到 out 文件夹。

./build/jadx/bin/jadx -d ./out ~/Desktop/decompiler.jar 
INFO  - loading ...
INFO  - processing ...
INFO  - doneress: 1143 of 1217 (93%)

Fernflower

GitHub 地址：https://github.com/fesh0r/fernflower Fernflower 和 Jadx 一样使用 Grade 进行依赖管理，可以自行克隆仓库打包运行。

➜  fernflower-master ./gradlew build

BUILD SUCCESSFUL in 32s
4 actionable tasks: 4 executed

➜  fernflower-master java -jar build/libs/fernflower.jar
Usage: java -jar fernflower.jar [-<option>=<value>]* [<source>]+ <destination>
Example: java -jar fernflower.jar -dgs=true c:\my\source\ c:\my.jar d:\decompiled\

➜  fernflower-master mkdir out
➜  fernflower-master java -jar build/libs/fernflower.jar ~/Desktop/decompiler.jar ./out
INFO:  Decompiling class com/strobel/assembler/metadata/ArrayTypeLoader
INFO:  ... done
INFO:  Decompiling class com/strobel/assembler/metadata/ParameterDefinition
INFO:  ... done
INFO:  Decompiling class com/strobel/assembler/metadata/MethodHandle
...

➜  fernflower-master ll out
total 1288
-rw-r--r--  1 darcy  staff   595K  5 16 17:47 decompiler.jar
➜  fernflower-master

Fernflower 在反编译 JAR 包时，默认反编译的结果也是一个 JAR 包。Jad

反编译速度

到这里已经介绍了五款 Java 反编译工具了，那么在日常开发中我们应该使用哪一个呢？又或者在代码分析时我们又该选择哪一个呢？我想这两种情况的不同，使用时的关注点也是不同的。如果是日常使用，读读代码，我想应该是对可读性要求更高些，如果是大量的代码分析工作，那么可能反编译的速度和语法的支持上要求更高些。为了能有一个简单的参考数据，我使用 JMH 微基准测试工具分别对这五款反编译工具进行了简单的测试，下面是一些测试结果。

测试环境

环境变量	描述
处理器	2.6 GHz 六核Intel Core i7
内存	16 GB 2667 MHz DDR4
Java 版本	JDK 14.0.2
测试方式	JMH 基准测试。
待反编译 JAR 1	procyon-compilertools-0.5.33.jar (1.5 MB)
待反编译 JAR 2	python2java4common-1.0.0-20180706.084921-1.jar (42 MB)

反编译 JAR 1：procyon-compilertools-0.5.33.jar (1.5 MB)

Benchmark	Mode	Cnt	Score	Units
cfr	avgt	10	6548.642 ± 363.502	ms/op
fernflower	avgt	10	12699.147 ± 1081.539	ms/op
jdcore	avgt	10	5728.621 ± 310.645	ms/op
procyon	avgt	10	26776.125 ± 2651.081	ms/op
jadx	avgt	10	7059.354 ± 323.351	ms/op

反编译 JAR 2: python2java4common-1.0.0-20180706.084921-1.jar (42 MB)

JAR 2 这个包是比较大的，是拿很多代码仓库合并到一起的，同时还有很多 Python 转 Java 生成的代码，理论上代码的复杂度会更高。

Benchmark	Cnt	Score
Cfr	1	413838.826ms
fernflower	1	246819.168ms
jdcore	1	Error
procyon	1	487647.181ms
jadx	1	505600.231ms

语法支持和可读性

如果反编译后的代码需要自己看的话，那么可读性更好的代码更占优势，下面我写了一些代码，主要是 Java 8 及以下的代码语法和一些嵌套的流程控制，看看反编译后的效果如何。

源码：

package com.wdbyte.decompiler;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;

import org.benf.cfr.reader.util.functors.UnaryFunction;

/**
 * @author https://www.wdbyte.com
 * @date 2021/05/16
 */
public class HardCode <A, B> {
    public HardCode(A a, B b) { }

    public static void test(int... args) { }

    public static void main(String... args) {
        test(1, 2, 3, 4, 5, 6);
    }

    int byteAnd0() {
        int b = 1;
        int x = 0;
        do {
            b = (byte)((b ^ x));
        } while (b++ < 10);
        return b;
    }

    private void a(Integer i) {
        a(i);
        b(i);
        c(i);
    }

    private void b(int i) {
        a(i);
        b(i);
        c(i);
    }

    private void c(double d) {
        c(d);
        d(d);
    }

    private void d(Double d) {
        c(d);
        d(d);
    }

    private void e(Short s) {
        b(s);
        c(s);
        e(s);
        f(s);
    }

    private void f(short s) {
        b(s);
        c(s);
        e(s);
        f(s);
    }

    void test1(String path) {
        try {
            int x = 3;
        } catch (NullPointerException t) {
            System.out.println("File Not found");
            if (path == null) { return; }
            throw t;
        } finally {
            System.out.println("Fred");
            if (path == null) { throw new IllegalStateException(); }
        }
    }

    private final List<Integer> stuff = new ArrayList<>();{
        stuff.add(1);
        stuff.add(2);
    }

    public static int plus(boolean t, int a, int b) {
        int c = t ? a : b;
        return c;
    }

    // Lambda
    Integer lambdaInvoker(int arg, UnaryFunction<Integer, Integer> fn) {
        return fn.invoke(arg);
    }

    // Lambda
    public int testLambda() {
        return lambdaInvoker(3, x -> x + 1);
        //        return 1;
    }

    // Lambda
    public Integer testLambda(List<Integer> stuff, int y, boolean b) {
        return stuff.stream().filter(b ? x -> x > y : x -> x < 3).findFirst().orElse(null);
    }

    // stream
    public static <Y extends Integer> void testStream(List<Y> list) {
        IntStream s = list.stream()
            .filter(x -> {
                System.out.println(x);
                return x.intValue() / 2 == 0;
                })
            .map(x -> (Integer)x+2)
            .mapToInt(x -> x);
        s.toArray();
    }

    // switch
    public void testSwitch1(){
        int i = 0;
        switch(((Long)(i + 1L)) + "") {
            case "1":
                System.out.println("one");
        }
    }
    // switch
    public void testSwitch2(String string){
        switch (string) {
            case "apples":
                System.out.println("apples");
                break;
            case "pears":
                System.out.println("pears");
                break;
        }
    }

    // switch
    public static void testSwitch3(int x) {
        while (true) {
            if (x < 5) {
                switch ("test") {
                    case "okay":
                        continue;
                    default:
                        continue;
                }
            }
            System.out.println("wow x2!");
        }
    }
}

Procyon 反编译：

package com.wdbyte.decompiler;

import java.util.*;
import org.benf.cfr.reader.util.functors.*;
import java.util.stream.*;

public class HardCode<A, B>
{
    private final List<Integer> stuff;
    
    public HardCode(final A a, final B b) {
        (this.stuff = new ArrayList<Integer>()).add(1);
        this.stuff.add(2);
    }
    
    public static void test(final int... args) {
    }
    
    public static void main(final String... args) {
        test(1, 2, 3, 4, 5, 6);
    }
    
    int byteAnd0() {
        int b = 1;
        final int x = 0;
        do {
            b = (byte)(b ^ x);
        } while (b++ < 10);
        return b;
    }
    
    private void a(final Integer i) {
        this.a(i);
        this.b(i);
        this.c(i);
    }
    
    private void b(final int i) {
        this.a(i);
        this.b(i);
        this.c(i);
    }
    
    private void c(final double d) {
        this.c(d);
        this.d(d);
    }
    
    private void d(final Double d) {
        this.c(d);
        this.d(d);
    }
    
    private void e(final Short s) {
        this.b(s);
        this.c(s);
        this.e(s);
        this.f(s);
    }
    
    private void f(final short s) {
        this.b(s);
        this.c(s);
        this.e(s);
        this.f(s);
    }
    
    void test1(final String path) {
        try {}
        catch (NullPointerException t) {
            System.out.println("File Not found");
            if (path == null) {
                return;
            }
            throw t;
        }
        finally {
            System.out.println("Fred");
            if (path == null) {
                throw new IllegalStateException();
            }
        }
    }
    
    public static int plus(final boolean t, final int a, final int b) {
        final int c = t ? a : b;
        return c;
    }
    
    Integer lambdaInvoker(final int arg, final UnaryFunction<Integer, Integer> fn) {
        return (Integer)fn.invoke((Object)arg);
    }
    
    public int testLambda() {
        return this.lambdaInvoker(3, (UnaryFunction<Integer, Integer>)(x -> x + 1));
    }
    
    public Integer testLambda(final List<Integer> stuff, final int y, final boolean b) {
        return stuff.stream().filter(b ? (x -> x > y) : (x -> x < 3)).findFirst().orElse(null);
    }
    
    public static <Y extends Integer> void testStream(final List<Y> list) {
        final IntStream s = list.stream().filter(x -> {
            System.out.println(x);
            return x / 2 == 0;
        }).map(x -> x + 2).mapToInt(x -> x);
        s.toArray();
    }
    
    public void testSwitch1() {
        final int i = 0;
        final String string = (Object)(i + 1L) + "";
        switch (string) {
            case "1": {
                System.out.println("one");
                break;
            }
        }
    }
    
    public void testSwitch2(final String string) {
        switch (string) {
            case "apples": {
                System.out.println("apples");
                break;
            }
            case "pears": {
                System.out.println("pears");
                break;
            }
        }
    }
    
    public static void testSwitch3(final int x) {
        while (true) {
            if (x < 5) {
                final String s = "test";
                switch (s) {
                    case "okay": {
                        continue;
                    }
                    default: {
                        continue;
                    }
                }
            }
            else {
                System.out.println("wow x2!");
            }
        }
    }
}

CFR 反编译：

/*
 * Decompiled with CFR 0.151.
 */
package com.wdbyte.decompiler;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;
import org.benf.cfr.reader.util.functors.UnaryFunction;

public class HardCode<A, B> {
    private final List<Integer> stuff = new ArrayList<Integer>();

    public HardCode(A a, B b) {
        this.stuff.add(1);
        this.stuff.add(2);
    }

    public static void test(int ... args) {
    }

    public static void main(String ... args) {
        HardCode.test(1, 2, 3, 4, 5, 6);
    }

    int byteAnd0() {
        byte by;
        byte b = 1;
        boolean x = false;
        do {
            by = b = (byte)(b ^ (x ? 1 : 0));
            b = (byte)(b + 1);
        } while (by < 10);
        return b;
    }

    private void a(Integer i) {
        this.a(i);
        this.b(i);
        this.c(i.intValue());
    }

    private void b(int i) {
        this.a(i);
        this.b(i);
        this.c(i);
    }

    private void c(double d) {
        this.c(d);
        this.d(d);
    }

    private void d(Double d) {
        this.c(d);
        this.d(d);
    }

    private void e(Short s) {
        this.b(s.shortValue());
        this.c(s.shortValue());
        this.e(s);
        this.f(s);
    }

    private void f(short s) {
        this.b(s);
        this.c(s);
        this.e(s);
        this.f(s);
    }

    void test1(String path) {
        try {
            int n = 3;
        }
        catch (NullPointerException t) {
            System.out.println("File Not found");
            if (path == null) {
                return;
            }
            throw t;
        }
        finally {
            System.out.println("Fred");
            if (path == null) {
                throw new IllegalStateException();
            }
        }
    }

    public static int plus(boolean t, int a, int b) {
        int c = t ? a : b;
        return c;
    }

    Integer lambdaInvoker(int arg, UnaryFunction<Integer, Integer> fn) {
        return fn.invoke(arg);
    }

    public int testLambda() {
        return this.lambdaInvoker(3, x -> x + 1);
    }

    public Integer testLambda(List<Integer> stuff, int y, boolean b) {
        return stuff.stream().filter(b ? x -> x > y : x -> x < 3).findFirst().orElse(null);
    }

    public static <Y extends Integer> void testStream(List<Y> list) {
        IntStream s = list.stream().filter(x -> {
            System.out.println(x);
            return x / 2 == 0;
        }).map(x -> x + 2).mapToInt(x -> x);
        s.toArray();
    }

    public void testSwitch1() {
        int i = 0;
        switch (Long.valueOf((long)i + 1L) + "") {
            case "1": {
                System.out.println("one");
            }
        }
    }

    public void testSwitch2(String string) {
        switch (string) {
            case "apples": {
                System.out.println("apples");
                break;
            }
            case "pears": {
                System.out.println("pears");
            }
        }
    }

    public static void testSwitch3(int x) {
        block6: while (true) {
            if (x < 5) {
                switch ("test") {
                    case "okay": {
                        continue block6;
                    }
                }
                continue;
            }
            System.out.println("wow x2!");
        }
    }
}

JD-CORE 反编译：

import com.wdbyte.decompiler.HardCode;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;
import org.benf.cfr.reader.util.functors.UnaryFunction;

public class HardCode<A, B> {
  private final List<Integer> stuff;
  
  public HardCode(A a, B b) {
    this.stuff = new ArrayList<>();
    this.stuff.add(Integer.valueOf(1));
    this.stuff.add(Integer.valueOf(2));
  }
  
  public static void test(int... args) {}
  
  public static void main(String... args) {
    test(new int[] { 1, 2, 3, 4, 5, 6 });
  }
  
  int byteAnd0() {
    int b = 1;
    int x = 0;
    while (true) {
      b = (byte)(b ^ x);
      if (b++ >= 10)
        return b; 
    } 
  }
  
  private void a(Integer i) {
    a(i);
    b(i.intValue());
    c(i.intValue());
  }
  
  private void b(int i) {
    a(Integer.valueOf(i));
    b(i);
    c(i);
  }
  
  private void c(double d) {
    c(d);
    d(Double.valueOf(d));
  }
  
  private void d(Double d) {
    c(d.doubleValue());
    d(d);
  }
  
  private void e(Short s) {
    b(s.shortValue());
    c(s.shortValue());
    e(s);
    f(s.shortValue());
  }
  
  private void f(short s) {
    b(s);
    c(s);
    e(Short.valueOf(s));
    f(s);
  }
  
  void test1(String path) {
    try {
      byte b = 3;
    } catch (NullPointerException t) {
      System.out.println("File Not found");
      if (path == null)
        return; 
      throw t;
    } finally {
      System.out.println("Fred");
      if (path == null)
        throw new IllegalStateException(); 
    } 
  }
  
  public static int plus(boolean t, int a, int b) {
    int c = t ? a : b;
    return c;
  }
  
  Integer lambdaInvoker(int arg, UnaryFunction<Integer, Integer> fn) {
    return (Integer)fn.invoke(Integer.valueOf(arg));
  }
  
  public int testLambda() {
    return lambdaInvoker(3, x -> Integer.valueOf(x.intValue() + 1)).intValue();
  }
  
  public Integer testLambda(List<Integer> stuff, int y, boolean b) {
    return stuff.stream().filter(b ? (x -> (x.intValue() > y)) : (x -> (x.intValue() < 3))).findFirst().orElse(null);
  }
  
  public static <Y extends Integer> void testStream(List<Y> list) {
    IntStream s = list.stream().filter(x -> {
          System.out.println(x);
          return (x.intValue() / 2 == 0);
        }).map(x -> Integer.valueOf(x.intValue() + 2)).mapToInt(x -> x.intValue());
    s.toArray();
  }
  
  public void testSwitch1() {
    int i = 0;
    switch (Long.valueOf(i + 1L) + "") {
      case "1":
        System.out.println("one");
        break;
    } 
  }
  
  public void testSwitch2(String string) {
    switch (string) {
      case "apples":
        System.out.println("apples");
        break;
      case "pears":
        System.out.println("pears");
        break;
    } 
  }
  
  public static void testSwitch3(int x) {
    while (true) {
      while (x < 5) {
        switch ("test") {
          case "okay":
            break;
        } 
      } 
      System.out.println("wow x2!");
    } 
  }
}

JadX 反编译：

package com.wdbyte.decompiler;

import java.util.ArrayList;
import java.util.List;
import org.benf.cfr.reader.util.functors.UnaryFunction;

/*  JADX ERROR: Class process error: JadxRuntimeException
    jadx.core.utils.exceptions.JadxRuntimeException: Code generation error after restart
    	at jadx.core.codegen.CodeGen.wrapCodeGen(CodeGen.java:52)
    	at jadx.core.codegen.CodeGen.generateJavaCode(CodeGen.java:34)
    	at jadx.core.codegen.CodeGen.generate(CodeGen.java:22)
    	at jadx.core.ProcessClass.process(ProcessClass.java:64)
    	at jadx.core.ProcessClass.generateCode(ProcessClass.java:88)
    	at jadx.core.dex.nodes.ClassNode.decompile(ClassNode.java:258)
    	at jadx.core.dex.nodes.ClassNode.decompile(ClassNode.java:221)
    Caused by: jadx.core.utils.exceptions.JadxRuntimeException: Method generation error
    	at jadx.core.codegen.ClassGen.addMethod(ClassGen.java:298)
    	at jadx.core.codegen.ClassGen.lambda$addInnerClsAndMethods$2(ClassGen.java:264)
    	at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
    	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
    	at java.base/java.util.stream.SortedOps$RefSortingSink.end(SortedOps.java:395)
    	at java.base/java.util.stream.Sink$ChainedReference.end(Sink.java:258)
    Caused by: jadx.core.utils.exceptions.CodegenException: Error generate insn: 0x001c: INVOKE  
      (wrap: java.util.stream.IntStream : 0x0018: INVOKE  (r0v0 's' java.util.stream.IntStream) = 
      (wrap: java.util.stream.Stream<R> : 0x0010: INVOKE  (r1v2 java.util.stream.Stream<R>) = 
      (wrap: java.util.stream.Stream<Y extends java.lang.Integer> : 0x0008: INVOKE  (r1v1 java.util.stream.Stream<Y extends java.lang.Integer>) = 
      (wrap: java.util.stream.Stream<Y extends java.lang.Integer> : 0x0000: INVOKE  (r1v0 java.util.stream.Stream<Y extends java.lang.Integer>) = (r3v0 'list' java.util.List<Y extends java.lang.Integer> A[D('list' java.util.List<Y extends java.lang.Integer>)]) type: INTERFACE call: java.util.List.stream():java.util.stream.Stream)
      (wrap: java.util.function.Predicate<? super Y extends java.lang.Integer> : 0x0007: MOVE_RESULT  (r2v0 java.util.function.Predicate<? super Y extends java.lang.Integer>) = )
     type: INTERFACE call: java.util.stream.Stream.filter(java.util.function.Predicate):java.util.stream.Stream)
      (wrap: java.util.function.Function<? super Y extends java.lang.Integer, ? extends R> : 0x000f: MOVE_RESULT  (r2v1 java.util.function.Function<? super Y extends java.lang.Integer, ? extends R>) = )
     type: INTERFACE call: java.util.stream.Stream.map(java.util.function.Function):java.util.stream.Stream)
      (wrap: java.util.function.ToIntFunction<? super R> : 0x0017: MOVE_RESULT  (r2v2 java.util.function.ToIntFunction<? super R>) = )
     type: INTERFACE call: java.util.stream.Stream.mapToInt(java.util.function.ToIntFunction):java.util.stream.IntStream)
     type: INTERFACE call: java.util.stream.IntStream.toArray():int[] in method: com.wdbyte.decompiler.HardCode.testStream(java.util.List<Y extends java.lang.Integer>):void, file: /var/folders/z4/q_08v96n28j2v3rgybvhytvr0000gp/T/jadx-10342693507538465510/classes.dex
    	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:255)
    	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:217)
    	at jadx.core.codegen.RegionGen.makeSimpleBlock(RegionGen.java:110)
    	at jadx.core.codegen.RegionGen.makeRegion(RegionGen.java:56)
    	at jadx.core.codegen.RegionGen.makeSimpleRegion(RegionGen.java:93)
    	at jadx.core.codegen.RegionGen.makeRegion(RegionGen.java:59)
    	at jadx.core.codegen.MethodGen.addRegionInsns(MethodGen.java:244)
    	at jadx.core.codegen.MethodGen.addInstructions(MethodGen.java:237)
    	at jadx.core.codegen.ClassGen.addMethodCode(ClassGen.java:342)
    	at jadx.core.codegen.ClassGen.addMethod(ClassGen.java:295)
    	... 5 more
    Caused by: jadx.core.utils.exceptions.CodegenException: Error generate insn: 0x0018: INVOKE  (r0v0 's' java.util.stream.IntStream) = 
      (wrap: java.util.stream.Stream<R> : 0x0010: INVOKE  (r1v2 java.util.stream.Stream<R>) = 
      (wrap: java.util.stream.Stream<Y extends java.lang.Integer> : 0x0008: INVOKE  (r1v1 java.util.stream.Stream<Y extends java.lang.Integer>) = 
      (wrap: java.util.stream.Stream<Y extends java.lang.Integer> : 0x0000: INVOKE  (r1v0 java.util.stream.Stream<Y extends java.lang.Integer>) = (r3v0 'list' java.util.List<Y extends java.lang.Integer> A[D('list' java.util.List<Y extends java.lang.Integer>)]) type: INTERFACE call: java.util.List.stream():java.util.stream.Stream)
      (wrap: java.util.function.Predicate<? super Y extends java.lang.Integer> : 0x0007: MOVE_RESULT  (r2v0 java.util.function.Predicate<? super Y extends java.lang.Integer>) = )
     type: INTERFACE call: java.util.stream.Stream.filter(java.util.function.Predicate):java.util.stream.Stream)
      (wrap: java.util.function.Function<? super Y extends java.lang.Integer, ? extends R> : 0x000f: MOVE_RESULT  (r2v1 java.util.function.Function<? super Y extends java.lang.Integer, ? extends R>) = )
     type: INTERFACE call: java.util.stream.Stream.map(java.util.function.Function):java.util.stream.Stream)
      (wrap: java.util.function.ToIntFunction<? super R> : 0x0017: MOVE_RESULT  (r2v2 java.util.function.ToIntFunction<? super R>) = )
     type: INTERFACE call: java.util.stream.Stream.mapToInt(java.util.function.ToIntFunction):java.util.stream.IntStream in method: com.wdbyte.decompiler.HardCode.testStream(java.util.List<Y extends java.lang.Integer>):void, file: /var/folders/z4/q_08v96n28j2v3rgybvhytvr0000gp/T/jadx-10342693507538465510/classes.dex
    	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:255)
    	at jadx.core.codegen.InsnGen.addWrappedArg(InsnGen.java:119)
    	at jadx.core.codegen.InsnGen.addArg(InsnGen.java:103)
    	at jadx.core.codegen.InsnGen.addArgDot(InsnGen.java:87)
    	at jadx.core.codegen.InsnGen.makeInvoke(InsnGen.java:715)
    	at jadx.core.codegen.InsnGen.makeInsnBody(InsnGen.java:367)
    	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:249)
    	... 14 more
    Caused by: jadx.core.utils.exceptions.CodegenException: Error generate insn: 0x0010: INVOKE  (r1v2 java.util.stream.Stream<R>) = 
      (wrap: java.util.stream.Stream<Y extends java.lang.Integer> : 0x0008: INVOKE  (r1v1 java.util.stream.Stream<Y extends java.lang.Integer>) = 
      (wrap: java.util.stream.Stream<Y extends java.lang.Integer> : 0x0000: INVOKE  (r1v0 java.util.stream.Stream<Y extends java.lang.Integer>) = (r3v0 'list' java.util.List<Y extends java.lang.Integer> A[D('list' java.util.List<Y extends java.lang.Integer>)]) type: INTERFACE call: java.util.List.stream():java.util.stream.Stream)
      (wrap: java.util.function.Predicate<? super Y extends java.lang.Integer> : 0x0007: MOVE_RESULT  (r2v0 java.util.function.Predicate<? super Y extends java.lang.Integer>) = )
     type: INTERFACE call: java.util.stream.Stream.filter(java.util.function.Predicate):java.util.stream.Stream)
      (wrap: java.util.function.Function<? super Y extends java.lang.Integer, ? extends R> : 0x000f: MOVE_RESULT  (r2v1 java.util.function.Function<? super Y extends java.lang.Integer, ? extends R>) = )
     type: INTERFACE call: java.util.stream.Stream.map(java.util.function.Function):java.util.stream.Stream in method: com.wdbyte.decompiler.HardCode.testStream(java.util.List<Y extends java.lang.Integer>):void, file: /var/folders/z4/q_08v96n28j2v3rgybvhytvr0000gp/T/jadx-10342693507538465510/classes.dex
    	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:255)
    	at jadx.core.codegen.InsnGen.addWrappedArg(InsnGen.java:119)
    	at jadx.core.codegen.InsnGen.addArg(InsnGen.java:103)
    	at jadx.core.codegen.InsnGen.addArgDot(InsnGen.java:87)
    	at jadx.core.codegen.InsnGen.makeInvoke(InsnGen.java:715)
    	at jadx.core.codegen.InsnGen.makeInsnBody(InsnGen.java:367)
    	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:230)
    	... 20 more
    Caused by: jadx.core.utils.exceptions.CodegenException: Error generate insn: 0x0008: INVOKE  (r1v1 java.util.stream.Stream<Y extends java.lang.Integer>) = 
      (wrap: java.util.stream.Stream<Y extends java.lang.Integer> : 0x0000: INVOKE  (r1v0 java.util.stream.Stream<Y extends java.lang.Integer>) = (r3v0 'list' java.util.List<Y extends java.lang.Integer> A[D('list' java.util.List<Y extends java.lang.Integer>)]) type: INTERFACE call: java.util.List.stream():java.util.stream.Stream)
      (wrap: java.util.function.Predicate<? super Y extends java.lang.Integer> : 0x0007: MOVE_RESULT  (r2v0 java.util.function.Predicate<? super Y extends java.lang.Integer>) = )
     type: INTERFACE call: java.util.stream.Stream.filter(java.util.function.Predicate):java.util.stream.Stream in method: com.wdbyte.decompiler.HardCode.testStream(java.util.List<Y extends java.lang.Integer>):void, file: /var/folders/z4/q_08v96n28j2v3rgybvhytvr0000gp/T/jadx-10342693507538465510/classes.dex
    	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:255)
    	at jadx.core.codegen.InsnGen.addWrappedArg(InsnGen.java:119)
    	at jadx.core.codegen.InsnGen.addArg(InsnGen.java:103)
    	at jadx.core.codegen.InsnGen.addArgDot(InsnGen.java:87)
    	at jadx.core.codegen.InsnGen.makeInvoke(InsnGen.java:715)
    	at jadx.core.codegen.InsnGen.makeInsnBody(InsnGen.java:367)
    	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:230)
    	... 26 more
    Caused by: jadx.core.utils.exceptions.CodegenException: Error generate insn: 0x0007: MOVE_RESULT  (r2v0 java.util.function.Predicate<? super Y extends java.lang.Integer>) =  in method: com.wdbyte.decompiler.HardCode.testStream(java.util.List<Y extends java.lang.Integer>):void, file: /var/folders/z4/q_08v96n28j2v3rgybvhytvr0000gp/T/jadx-10342693507538465510/classes.dex
    	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:255)
    	at jadx.core.codegen.InsnGen.addWrappedArg(InsnGen.java:119)
    	at jadx.core.codegen.InsnGen.addArg(InsnGen.java:103)
    	at jadx.core.codegen.InsnGen.generateMethodArguments(InsnGen.java:806)
    	at jadx.core.codegen.InsnGen.makeInvoke(InsnGen.java:746)
    	at jadx.core.codegen.InsnGen.makeInsnBody(InsnGen.java:367)
    	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:230)
    	... 32 more
    Caused by: jadx.core.utils.exceptions.CodegenException: MOVE_RESULT instruction can be used only in fallback mode
    	at jadx.core.codegen.InsnGen.fallbackOnlyInsn(InsnGen.java:604)
    	at jadx.core.codegen.InsnGen.makeInsnBody(InsnGen.java:542)
    	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:230)
    	... 38 more
    */
public class HardCode<A, B> {
    private final List<Integer> stuff = new ArrayList();

    public HardCode(A a, B b) {
        this.stuff.add(1);
        this.stuff.add(2);
    }

    public static void test(int... args) {
    }

    public static void main(String... args) {
        test(1, 2, 3, 4, 5, 6);
    }

    /* access modifiers changed from: package-private */
    public int byteAnd0() {
        int b = 1;
        while (true) {
            int b2 = (byte) (b ^ 0);
            int b3 = b2 + 1;
            if (b2 >= 10) {
                return b3;
            }
            b = b3;
        }
    }

    private void a(Integer i) {
        a(i);
        b(i.intValue());
        c((double) i.intValue());
    }

    private void b(int i) {
        a(Integer.valueOf(i));
        b(i);
        c((double) i);
    }

    private void c(double d) {
        c(d);
        d(Double.valueOf(d));
    }

    private void d(Double d) {
        c(d.doubleValue());
        d(d);
    }

    private void e(Short s) {
        b(s.shortValue());
        c((double) s.shortValue());
        e(s);
        f(s.shortValue());
    }

    private void f(short s) {
        b(s);
        c((double) s);
        e(Short.valueOf(s));
        f(s);
    }

    /* access modifiers changed from: package-private */
    public void test1(String path) {
        System.out.println("Fred");
        if (path == null) {
            throw new IllegalStateException();
        }
    }

    public static int plus(boolean t, int a, int b) {
        return t ? a : b;
    }

    /* access modifiers changed from: package-private */
    public Integer lambdaInvoker(int arg, UnaryFunction<Integer, Integer> fn) {
        return (Integer) fn.invoke(Integer.valueOf(arg));
    }

    public int testLambda() {
        /*
            r2 = this;
            r0 = 3
            r1 = move-result
            java.lang.Integer r0 = r2.lambdaInvoker(r0, r1)
            int r0 = r0.intValue()
            return r0
        */
        throw new UnsupportedOperationException("Method not decompiled: com.wdbyte.decompiler.HardCode.testLambda():int");
    }

    private static /* synthetic */ boolean lambda$testLambda$1(int y, Integer x) {
        return x.intValue() > y;
    }

    private static /* synthetic */ boolean lambda$testLambda$2(Integer x) {
        return x.intValue() < 3;
    }

    public java.lang.Integer testLambda(java.util.List<java.lang.Integer> r3, int r4, boolean r5) {
        /*
            r2 = this;
            java.util.stream.Stream r1 = r3.stream()
            if (r5 == 0) goto L_0x001a
            r0 = move-result
        L_0x000a:
            java.util.stream.Stream r0 = r1.filter(r0)
            java.util.Optional r0 = r0.findFirst()
            r1 = 0
            java.lang.Object r0 = r0.orElse(r1)
            java.lang.Integer r0 = (java.lang.Integer) r0
            return r0
        L_?:
            r0 = move-result
            goto L_0x000a
        */
        throw new UnsupportedOperationException("Method not decompiled: com.wdbyte.decompiler.HardCode.testLambda(java.util.List, int, boolean):java.lang.Integer");
    }

    /*  JADX ERROR: MOVE_RESULT instruction can be used only in fallback mode
        jadx.core.utils.exceptions.CodegenException: MOVE_RESULT instruction can be used only in fallback mode
        	at jadx.core.codegen.InsnGen.fallbackOnlyInsn(InsnGen.java:604)
        	at jadx.core.codegen.InsnGen.makeInsnBody(InsnGen.java:542)
        	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:230)
        	at jadx.core.codegen.InsnGen.addWrappedArg(InsnGen.java:119)
        	at jadx.core.codegen.InsnGen.addArg(InsnGen.java:103)
        	at jadx.core.codegen.InsnGen.generateMethodArguments(InsnGen.java:806)
        	at jadx.core.codegen.InsnGen.makeInvoke(InsnGen.java:746)
        	at jadx.core.codegen.InsnGen.makeInsnBody(InsnGen.java:367)
        	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:230)
        	at jadx.core.codegen.InsnGen.addWrappedArg(InsnGen.java:119)
        	at jadx.core.codegen.InsnGen.addArg(InsnGen.java:103)
        	at jadx.core.codegen.InsnGen.addArgDot(InsnGen.java:87)
        	at jadx.core.codegen.InsnGen.makeInvoke(InsnGen.java:715)
        	at jadx.core.codegen.InsnGen.makeInsnBody(InsnGen.java:367)
        	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:230)
        	at jadx.core.codegen.InsnGen.addWrappedArg(InsnGen.java:119)
        	at jadx.core.codegen.InsnGen.addArg(InsnGen.java:103)
        	at jadx.core.codegen.InsnGen.addArgDot(InsnGen.java:87)
        	at jadx.core.codegen.InsnGen.makeInvoke(InsnGen.java:715)
        	at jadx.core.codegen.InsnGen.makeInsnBody(InsnGen.java:367)
        	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:230)
        	at jadx.core.codegen.InsnGen.addWrappedArg(InsnGen.java:119)
        	at jadx.core.codegen.InsnGen.addArg(InsnGen.java:103)
        	at jadx.core.codegen.InsnGen.addArgDot(InsnGen.java:87)
        	at jadx.core.codegen.InsnGen.makeInvoke(InsnGen.java:715)
        	at jadx.core.codegen.InsnGen.makeInsnBody(InsnGen.java:367)
        	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:249)
        	at jadx.core.codegen.InsnGen.makeInsn(InsnGen.java:217)
        	at jadx.core.codegen.RegionGen.makeSimpleBlock(RegionGen.java:110)
        	at jadx.core.codegen.RegionGen.makeRegion(RegionGen.java:56)
        	at jadx.core.codegen.RegionGen.makeSimpleRegion(RegionGen.java:93)
        	at jadx.core.codegen.RegionGen.makeRegion(RegionGen.java:59)
        	at jadx.core.codegen.MethodGen.addRegionInsns(MethodGen.java:244)
        	at jadx.core.codegen.MethodGen.addInstructions(MethodGen.java:237)
        	at jadx.core.codegen.ClassGen.addMethodCode(ClassGen.java:342)
        	at jadx.core.codegen.ClassGen.addMethod(ClassGen.java:295)
        	at jadx.core.codegen.ClassGen.lambda$addInnerClsAndMethods$2(ClassGen.java:264)
        	at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
        	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
        	at java.base/java.util.stream.SortedOps$RefSortingSink.end(SortedOps.java:395)
        	at java.base/java.util.stream.Sink$ChainedReference.end(Sink.java:258)
        */
    public static <Y extends java.lang.Integer> void testStream(java.util.List<Y> r3) {
        /*
            java.util.stream.Stream r1 = r3.stream()
            r2 = move-result
            java.util.stream.Stream r1 = r1.filter(r2)
            r2 = move-result
            java.util.stream.Stream r1 = r1.map(r2)
            r2 = move-result
            java.util.stream.IntStream r0 = r1.mapToInt(r2)
            r0.toArray()
            return
        */
        throw new UnsupportedOperationException("Method not decompiled: com.wdbyte.decompiler.HardCode.testStream(java.util.List):void");
    }

    private static /* synthetic */ boolean lambda$testStream$3(Integer x) {
        System.out.println(x);
        return x.intValue() / 2 == 0;
    }

    public void testSwitch1() {
        String str = Long.valueOf(((long) 0) + 1) + "";
        char c = 65535;
        switch (str.hashCode()) {
            case 49:
                if (str.equals("1")) {
                    c = 0;
                    break;
                }
                break;
        }
        switch (c) {
            case 0:
                System.out.println("one");
                return;
            default:
                return;
        }
    }

    public void testSwitch2(String string) {
        char c = 65535;
        switch (string.hashCode()) {
            case -1411061671:
                if (string.equals("apples")) {
                    c = 0;
                    break;
                }
                break;
            case 106540109:
                if (string.equals("pears")) {
                    c = 1;
                    break;
                }
                break;
        }
        switch (c) {
            case 0:
                System.out.println("apples");
                return;
            case 1:
                System.out.println("pears");
                return;
            default:
                return;
        }
    }

    public static void testSwitch3(int x) {
        while (true) {
            if (x < 5) {
                char c = 65535;
                switch ("test".hashCode()) {
                    case 3412756:
                        if ("test".equals("okay")) {
                            c = 0;
                            break;
                        }
                        break;
                }
                switch (c) {
                }
            } else {
                System.out.println("wow x2!");
            }
        }
    }
}

Fernflower 反编译：

package com.wdbyte.decompiler;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;
import org.benf.cfr.reader.util.functors.UnaryFunction;

public class HardCode {
   private final List stuff = new ArrayList();

   public HardCode(Object a, Object b) {
      this.stuff.add(1);
      this.stuff.add(2);
   }

   public static void test(int... args) {
   }

   public static void main(String... args) {
      test(1, 2, 3, 4, 5, 6);
   }

   int byteAnd0() {
      int b = 1;
      byte x = 0;

      byte var10000;
      do {
         int b = (byte)(b ^ x);
         var10000 = b;
         b = b + 1;
      } while(var10000 < 10);

      return b;
   }

   private void a(Integer i) {
      this.a(i);
      this.b(i);
      this.c((double)i);
   }

   private void b(int i) {
      this.a(i);
      this.b(i);
      this.c((double)i);
   }

   private void c(double d) {
      this.c(d);
      this.d(d);
   }

   private void d(Double d) {
      this.c(d);
      this.d(d);
   }

   private void e(Short s) {
      this.b(s);
      this.c((double)s);
      this.e(s);
      this.f(s);
   }

   private void f(short s) {
      this.b(s);
      this.c((double)s);
      this.e(s);
      this.f(s);
   }

   void test1(String path) {
      try {
         boolean var2 = true;
         return;
      } catch (NullPointerException var6) {
         System.out.println("File Not found");
         if (path != null) {
            throw var6;
         }
      } finally {
         System.out.println("Fred");
         if (path == null) {
            throw new IllegalStateException();
         }

      }

   }

   public static int plus(boolean t, int a, int b) {
      int c = t ? a : b;
      return c;
   }

   Integer lambdaInvoker(int arg, UnaryFunction fn) {
      return (Integer)fn.invoke(arg);
   }

   public int testLambda() {
      return this.lambdaInvoker(3, (x) -> {
         return x + 1;
      });
   }

   public Integer testLambda(List stuff, int y, boolean b) {
      return (Integer)stuff.stream().filter(b ? (x) -> {
         return x > y;
      } : (x) -> {
         return x < 3;
      }).findFirst().orElse((Object)null);
   }

   public static void testStream(List list) {
      IntStream s = list.stream().filter((x) -> {
         System.out.println(x);
         return x / 2 == 0;
      }).map((x) -> {
         return x + 2;
      }).mapToInt((x) -> {
         return x;
      });
      s.toArray();
   }

   public void testSwitch1() {
      int i = 0;
      String var2 = (long)i + 1L + "";
      byte var3 = -1;
      switch(var2.hashCode()) {
      case 49:
         if (var2.equals("1")) {
            var3 = 0;
         }
      default:
         switch(var3) {
         case 0:
            System.out.println("one");
         default:
         }
      }
   }

   public void testSwitch2(String string) {
      byte var3 = -1;
      switch(string.hashCode()) {
      case -1411061671:
         if (string.equals("apples")) {
            var3 = 0;
         }
         break;
      case 106540109:
         if (string.equals("pears")) {
            var3 = 1;
         }
      }

      switch(var3) {
      case 0:
         System.out.println("apples");
         break;
      case 1:
         System.out.println("pears");
      }

   }

   public static void testSwitch3(int x) {
      while(true) {
         if (x < 5) {
            String var1 = "test";
            byte var2 = -1;
            switch(var1.hashCode()) {
            case 3412756:
               if (var1.equals("okay")) {
                  var2 = 0;
              }
            default:
               switch(var2) {
               case 0:
               }
            }
         } else {
            System.out.println("wow x2!");
         }
      }
   }
}

Procyon

看到 Procyon 的反编译结果，还是比较吃惊的，在正常反编译的情况下，反编译后的代码基本上都是原汁原味。唯一一处反编译后和源码语法上有变化的地方，是一个集合的初始化操作略有不同。

待反编译源码：

// 源码
 public HardCode(A a, B b) { }
 private final List<Integer> stuff = new ArrayList<>();{
    stuff.add(1);
    stuff.add(2);
 }

Procyon 反编译：

// Procyon 反编译
private final List<Integer> stuff;
    
public HardCode(final A a, final B b) {
    (this.stuff = new ArrayList<Integer>()).add(1);
    this.stuff.add(2);
}

而其他部分代码，比如装箱拆箱，Switch 语法，Lambda 表达式，流式操作以及流程控制等，几乎完全一致，阅读没有障碍。

装箱拆箱操作反编译后完全一致，没有多余的类型转换代码。

待反编译源码：

// 源码
private void a(Integer i) {
    a(i);
    b(i);
    c(i);
}

private void b(int i) {
    a(i);
    b(i);
    c(i);
}

private void c(double d) {
    c(d);
    d(d);
}

private void d(Double d) {
    c(d);
    d(d);
}

private void e(Short s) {
    b(s);
    c(s);
    e(s);
    f(s);
}

private void f(short s) {
    b(s);
    c(s);
    e(s);
    f(s);
}

Procyon 反编译：

// Procyon 反编译
private void a(final Integer i) {
    this.a(i);
    this.b(i);
    this.c(i);
}

private void b(final int i) {
    this.a(i);
    this.b(i);
    this.c(i);
}

private void c(final double d) {
    this.c(d);
    this.d(d);
}

private void d(final Double d) {
    this.c(d);
    this.d(d);
}

private void e(final Short s) {
    this.b(s);
    this.c(s);
    this.e(s);
    this.f(s);
}

private void f(final short s) {
    this.b(s);
    this.c(s);
    this.e(s);
    this.f(s);
}

Switch 部分也是一致，流程控制部分也没有变化。

待反编译源码：

// 源码 switch
public void testSwitch1(){
    int i = 0;
    switch(((Long)(i + 1L)) + "") {
        case "1":
            System.out.println("one");
    }
}
public void testSwitch2(String string){
    switch (string) {
        case "apples":
            System.out.println("apples");
            break;
        case "pears":
            System.out.println("pears");
            break;
    }
}
public static void testSwitch3(int x) {
    while (true) {
        if (x < 5) {
            switch ("test") {
                case "okay":
                    continue;
                default:
                    continue;
            }
        }
        System.out.println("wow x2!");
    }
}

Procyon 反编译：

// Procyon 反编译
public void testSwitch1() {
    final int i = 0;
    final String string = (Object)(i + 1L) + "";
    switch (string) {
        case "1": {
            System.out.println("one");
            break;
        }
    }
}
public void testSwitch2(final String string) {
    switch (string) {
        case "apples": {
            System.out.println("apples");
            break;
        }
        case "pears": {
            System.out.println("pears");
            break;
        }
    }
}   
public static void testSwitch3(final int x) {
    while (true) {
        if (x < 5) {
            final String s = "test";
            switch (s) {
                case "okay": {
                    continue;
                }
                default: {
                    continue;
                }
            }
        }
        else {
            System.out.println("wow x2!");
        }
    }
}

Lambda 表达式和流式操作完全一致。

源码：

// 源码
// Lambda
public Integer testLambda(List<Integer> stuff, int y, boolean b) {
    return stuff.stream().filter(b ? x -> x > y : x -> x < 3).findFirst().orElse(null);
}

// stream
public static <Y extends Integer> void testStream(List<Y> list) {
    IntStream s = list.stream()
        .filter(x -> {
            System.out.println(x);
            return x.intValue() / 2 == 0;
            })
        .map(x -> (Integer)x+2)
        .mapToInt(x -> x);
    s.toArray();
}

Procyon 反编译：

// Procyon 反编译
public Integer testLambda(final List<Integer> stuff, final int y, final boolean b) {
    return stuff.stream().filter(b ? (x -> x > y) : (x -> x < 3)).findFirst().orElse(null);
}

public static <Y extends Integer> void testStream(final List<Y> list) {
    final IntStream s = list.stream().filter(x -> {
        System.out.println(x);
        return x / 2 == 0;
    }).map(x -> x + 2).mapToInt(x -> x);
    s.toArray();
}

流程控制，反编译后发现丢失了无意义的代码部分，阅读来说并无障碍。

源码：

// 源码
void test1(String path) {
    try {
        int x = 3;
    } catch (NullPointerException t) {
        System.out.println("File Not found");
        if (path == null) { return; }
        throw t;
    } finally {
        System.out.println("Fred");
        if (path == null) { throw new IllegalStateException(); }
    }
}

Procyon 反编译：

// Procyon 反编译
void test1(final String path) {
    try {}
    catch (NullPointerException t) {
        System.out.println("File Not found");
        if (path == null) {
            return;
        }
        throw t;
    }
    finally {
        System.out.println("Fred");
        if (path == null) {
            throw new IllegalStateException();
        }
    }
}

鉴于代码篇幅，下面几种的反编译结果的对比只会列出不同之处，相同之处会直接跳过。

CFR

CFR 的反编译结果多出了类型转换部分，个人来看没有 Procyon 那么原汁原味，不过也算是十分优秀，测试案例中唯一不满意的地方是对 while continue 的处理。

// CFR 反编译结果
// 装箱拆箱
private void e(Short s) {
   this.b(s.shortValue()); // 装箱拆箱多出了类型转换部分。
   this.c(s.shortValue()); // 装箱拆箱多出了类型转换部分。
   this.e(s);
   this.f(s);
}
// 流程控制
void test1(String path) {
    try {
        int n = 3;// 流程控制反编译结果十分满意，原汁原味，甚至此处的无意思代码都保留了。
    }
    catch (NullPointerException t) {
        System.out.println("File Not found");
        if (path == null) {
            return;
        }
        throw t;
    }
    finally {
        System.out.println("Fred");
        if (path == null) {
            throw new IllegalStateException();
        }
    }
}
// Lambda 和 Stream 操作完全一致，不提。
// switch 处，反编译后功能一致，但是流程控制有所更改。
public static void testSwitch3(int x) {
    block6: while (true) { // 源码中只有 while(true)，反编译后多了 block6
        if (x < 5) {
            switch ("test") {
                case "okay": {
                    continue block6; // 多了 block6
                }
            }
            continue;
        }
        System.out.println("wow x2!");
    }
}

JD-Core

JD-Core 和 CFR 一样，对于装箱拆箱操作，反编译后不再一致，多了类型转换部分，而且自动优化了数据类型。个人感觉，如果是反编译后自己阅读，通篇的数据类型的转换优化影响还是挺大的。

// JD-Core 反编译
private void d(Double d) {
  c(d.doubleValue()); // 新增了数据类型转换
  d(d);
}

private void e(Short s) {
  b(s.shortValue()); // 新增了数据类型转换
  c(s.shortValue()); // 新增了数据类型转换
  e(s);
  f(s.shortValue()); // 新增了数据类型转换
}

private void f(short s) {
  b(s);
  c(s);
  e(Short.valueOf(s)); // 新增了数据类型转换
  f(s);
}
// Stream 操作中，也自动优化了数据类型转换，阅读起来比较累。
public static <Y extends Integer> void testStream(List<Y> list) {
  IntStream s = list.stream().filter(x -> {
        System.out.println(x);
        return (x.intValue() / 2 == 0);
      }).map(x -> Integer.valueOf(x.intValue() + 2)).mapToInt(x -> x.intValue());
  s.toArray();
}

Jadx

首先 Jadx 在反编译测试代码时，报出了错误，反编译的结果里也有提示不能反编 Lambda 和 Stream 操作，反编译结果中变量名称杂乱无章，流程控制几乎阵亡，如果你想反编译后生物肉眼阅读，Jadx 肯定不是一个好选择。

// Jadx 反编译
private void e(Short s) {
    b(s.shortValue());// 新增了数据类型转换
    c((double) s.shortValue());// 新增了数据类型转换
    e(s);
    f(s.shortValue());// 新增了数据类型转换
}

private void f(short s) {
    b(s);
    c((double) s);// 新增了数据类型转换
    e(Short.valueOf(s));// 新增了数据类型转换
    f(s);
}
public int testLambda() { // testLambda 反编译失败
    /*
        r2 = this;
        r0 = 3
        r1 = move-result
        java.lang.Integer r0 = r2.lambdaInvoker(r0, r1)
        int r0 = r0.intValue()
        return r0
    */
    throw new UnsupportedOperationException("Method not decompiled: com.wdbyte.decompiler.HardCode.testLambda():int");
}
// Stream 反编译失败
public static <Y extends java.lang.Integer> void testStream(java.util.List<Y> r3) {
    /*
        java.util.stream.Stream r1 = r3.stream()
        r2 = move-result
        java.util.stream.Stream r1 = r1.filter(r2)
        r2 = move-result
        java.util.stream.Stream r1 = r1.map(r2)
        r2 = move-result
        java.util.stream.IntStream r0 = r1.mapToInt(r2)
        r0.toArray()
        return
    */
    throw new UnsupportedOperationException("Method not decompiled: com.wdbyte.decompiler.HardCode.testStream(java.util.List):void");
}
public void testSwitch2(String string) { // switch 操作无法正常阅读，和源码出入较大。
    char c = 65535;
    switch (string.hashCode()) {
        case -1411061671:
            if (string.equals("apples")) {
                c = 0;
                break;
            }
            break;
        case 106540109:
            if (string.equals("pears")) {
                c = 1;
                break;
            }
            break;
    }
    switch (c) {
        case 0:
            System.out.println("apples");
            return;
        case 1:
            System.out.println("pears");
            return;
        default:
            return;
    }
}

Fernflower

Fernflower 的反编译结果总体上还是不错的，不过也有不足，它对变量名称的指定，以及 Switch 字符串时的反编译结果不够理想。

//反编译后变量命名不利于阅读，有很多 var 变量
int byteAnd0() {
   int b = 1;
   byte x = 0;

   byte var10000;
   do {
      int b = (byte)(b ^ x);
      var10000 = b;
      b = b + 1;
   } while(var10000 < 10);

   return b;
}
// switch 反编译结果使用了hashCode
public static void testSwitch3(int x) {
   while(true) {
      if (x < 5) {
         String var1 = "test";
         byte var2 = -1;
         switch(var1.hashCode()) {
         case 3412756: 
            if (var1.equals("okay")) {
               var2 = 0;
           }
         default:
            switch(var2) {
            case 0:
            }
         }
      } else {
         System.out.println("wow x2!");
      }
   }
}

总结

五种反编译工具比较下来，结合反编译速度和代码可读性测试，看起来 CFR 工具胜出，Procyon 紧随其后。CFR 在速度上不落下风，在反编译的代码可读性上，是最好的，主要体现在反编译后的变量命名、装箱拆箱、类型转换，流程控制上，以及对 Lambda 表达式、Stream 流式操作和 Switch 的语法支持上，都非常优秀。根据 CFR 官方介绍，已经支持到 Java 14 语法，而且截止写这篇测试文章时，CFR 最新提交代码时间实在 11 小时之前，更新速度很快。

文章中部分代码已经上传 GitHub ：github.com/niumoo/lab-notes/tree/master/java-decompiler

Java 反编译工具的使用与对比分析

前言

Procyon

使用 Procyon

Procyon GUI

CFR​

CFR 命令行使用

CFR 代码中使用

JD-Core

使用 JD-core

JD-GUI

Jadx

Fernflower

反编译速度

语法支持和可读性

Procyon

CFR

JD-Core

Jadx

Fernflower

总结

CFR