Java是当今最流行的编程语言之一,而javap是Java开发工具包（JDK）中一个强大的命令行工具，用于反汇编.class文件，通过使用javap，开发者可以深入了解Java字节码，这对于理解Java虚拟机（JVM）的工作原理以及优化Java程序性能至关重要，本文将详细介绍如何使用javap，并提供一些经验案例。
安装Java开发工具包（JDK）
在使用javap之前，确保您的计算机上已安装Java开发工具包（JDK），您可以从Oracle官方网站下载最新版本的JDK。
打开命令行窗口
在Windows系统中,按下Win + R键，输入cmd并按回车，在macOS或Linux系统中，打开终端。
使用javap命令
在命令行窗口中,输入以下命令：
javap -c [class文件路径]
-c选项表示以汇编代码的形式显示类文件的内容。[class文件路径]是您要反汇编的.class文件的路径。
解释输出结果
javap命令的输出结果通常包括以下部分：
- 类名和版本信息
- 类的访问修饰符（如public、private等）
- 类的父类和实现的接口
- 字段信息
- 方法信息
以下是一个简单的例子：
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}
反汇编后的输出结果如下：
public class HelloWorld
minor version: 0
major version: 52
flags: ACC_PUBLIC, ACC_SUPER
super: java/lang/Object
interfaces: 0
fields:
public static final java.lang.String $CLASS$ : Ljava/lang/String;
public static final java.lang.String $MODULE$ : Ljava/lang/String;
public static final java.lang.String $PACKAGE$ : Ljava/lang/String;
public static final java.lang.String $SB$ : Ljava/lang/StringBuilder;
public static final java.lang.String $S : Ljava/lang/String;
public static final java.lang.String $T : Ljava/lang/String;
public static final java.lang.String $TM$ : Ljava/lang/String;
public static final java.lang.String $TN$ : Ljava/lang/String;
public static final java.lang.String $TT$ : Ljava/lang/String;
public static final java.lang.String $TTN$ : Ljava/lang/String;
public static final java.lang.String $TTTN$ : Ljava/lang/String;
public static final java.lang.String $TNT$ : Ljava/lang/String;
public static final java.lang.String $TNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNT$ : Ljava/lang/String;
public static final java.lang.String $TNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTNTN$ : Ljava/lang/String;
public static final java.lang.String $TNTNT
