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新建Decompilation.java文件

public class Decompilation {
    private Object object = new Object();

    public void insert(Thread thread) {
        synchronized (object) {

        }
    }
}

编译

javac Decompilation.java

反编译获得字节码指令

javap -verbose Decompilation.class

 public void insert(java.lang.Thread);
    descriptor: (Ljava/lang/Thread;)V
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=4, args_size=2
         0: aload_0
         1: getfield      #3                  // Field object:Ljava/lang/Object;
         4: dup
         5: astore_2
         6: monitorenter               // 要获取到锁
         7: aload_2
         8: monitorexit                // 释放锁
         9: goto          17
        12: astore_3
        13: aload_2
        14: monitorexit               // 释放锁，第二个出口。一个锁入口，两个锁出口（正常退出 + 异常退出）
        15: aload_3
        16: athrow
        17: return
      Exception table:
         from    to  target type
             7     9    12   any
            12    15    12   any
      LineNumberTable:
        line 5: 0
        line 7: 7
        line 8: 17
      StackMapTable: number_of_entries = 2
        frame_type = 255 /* full_frame */
          offset_delta = 12
          locals = [ class Decompilation, class java/lang/Thread, class java/lang/Object ]
          stack = [ class java/lang/Throwable ]
        frame_type = 250 /* chop */
          offset_delta = 4