synchronized 關鍵字鎖淺析

1. 編寫java代碼

package com.seeyon.test;

/**
 * @Author: 
 * @CreateTime: 2022-1-9 21:59
 * @Description:
 */
public class SynTest {

    public  void synBlock() {
        synchronized (this) {
            System.out.println("synchronized 詳解");
        }
    }
}      

D:\open_source\DXZW\src\com\seeyon\test>javac SynTest.java

D:\open_source\DXZW\src\com\seeyon\test>javap -verbose SynTest.class
Classfile /D:/open_source/DXZW/src/com/seeyon/test/SynTest.class
  Last modified 2022-1-9; size 536 bytes
  MD5 checksum 90124e59d243d5c40b89635d570db246
  Compiled from "SynTest.java"
public class com.seeyon.test.SynTest
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Methodref          #6.#18         // java/lang/Object."<init>":()V
   #2 = Fieldref           #19.#20        // java/lang/System.out:Ljava/io/PrintStream;
   #3 = String             #21            // synchronized 璇﹁В
   #4 = Methodref          #22.#23        // java/io/PrintStream.println:(Ljava/lang/String;)V
   #5 = Class              #24            // com/seeyon/test/SynTest
   #6 = Class              #25            // java/lang/Object
   #7 = Utf8               <init>
   #8 = Utf8               ()V
   #9 = Utf8               Code
  #10 = Utf8               LineNumberTable
  #11 = Utf8               synBlock
  #12 = Utf8               StackMapTable
  #13 = Class              #24            // com/seeyon/test/SynTest
  #14 = Class              #25            // java/lang/Object
  #15 = Class              #26            // java/lang/Throwable
  #16 = Utf8               SourceFile
  #17 = Utf8               SynTest.java
  #18 = NameAndType        #7:#8          // "<init>":()V
  #19 = Class              #27            // java/lang/System
  #20 = NameAndType        #28:#29        // out:Ljava/io/PrintStream;
  #21 = Utf8               synchronized 璇﹁В
  #22 = Class              #30            // java/io/PrintStream
  #23 = NameAndType        #31:#32        // println:(Ljava/lang/String;)V
  #24 = Utf8               com/seeyon/test/SynTest
  #25 = Utf8               java/lang/Object
  #26 = Utf8               java/lang/Throwable
  #27 = Utf8               java/lang/System
  #28 = Utf8               out
  #29 = Utf8               Ljava/io/PrintStream;
  #30 = Utf8               java/io/PrintStream
  #31 = Utf8               println
  #32 = Utf8               (Ljava/lang/String;)V
{
  public com.seeyon.test.SynTest();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial #1                  // Method java/lang/Object."<init>":()V
         4: return
      LineNumberTable:
        line 8: 0

  public void synBlock();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=3, args_size=1
         0: aload_0
         1: dup
         2: astore_1
         3: monitorenter
         4: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
         7: ldc           #3                  // String synchronized 璇﹁В
         9: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
        12: aload_1
        13: monitorexit
        14: goto          22
        17: astore_2
        18: aload_1
        19: monitorexit
        20: aload_2
        21: athrow
        22: return
      Exception table:
         from    to  target type
             4    14    17   any
            17    20    17   any
      LineNumberTable:
        line 11: 0
        line 12: 4
        line 13: 12
        line 14: 22
      StackMapTable: number_of_entries = 2
        frame_type = 255 /* full_frame */
          offset_delta = 17
          locals = [ class com/seeyon/test/SynTest, class java/lang/Object ]
          stack = [ class java/lang/Throwable ]
        frame_type = 250 /* chop */
          offset_delta = 4
}
SourceFile: "SynTest.java"