🚀 JVM方法区与运行时常量池详解

/*=== Java反编译结果 (javap 命令输出) ===*/
// 使用命令: javap -verbose HelloWorld.class
// 查看字节码: javap -c HelloWorld.class

Compiled from "HelloWorld.java"
public class HelloWorld {
  // 默认构造方法
  public HelloWorld();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0           // 加载this引用到操作数栈
         1: invokespecial #1  // 调用Object构造方法，#1指向常量池
         4: return            // 方法返回

  // main方法 - 程序入口
  public static void main(java.lang.String[]);
    descriptor: ([Ljava/lang/String;)V
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=2, locals=1, args_size=1
         0: getstatic     #2  // 获取System.out字段，#2指向常量池
         3: ldc           #3  // 加载字符串常量到栈，#3指向常量池
         5: invokevirtual #4  // 调用println方法，#4指向常量池
         8: return            // 方法返回

// 运行时常量池详细信息
Constant pool:
   #1 = Methodref          #6.#15         // java/lang/Object."<init>":()V
   #2 = Fieldref           #16.#17        // java/lang/System.out:Ljava/io/PrintStream;
   #3 = String             #18            // "Hello World"
   #4 = Methodref          #19.#20        // java/io/PrintStream.println:(Ljava/lang/String;)V
   #5 = Class              #21            // HelloWorld
   #6 = Class              #22            // java/lang/Object
   #7 = Utf8               <init>
   #8 = Utf8               ()V
   ...
}