Java对象组成查看信息

拼搏现实的明天。 2023-01-08 13:30 215阅读 0赞

## 查看对象的组成信息 ##

包括偏向状态，锁状态标志，对齐填充，实例大小，空间损耗

<dependency>
                <groupId>org.openjdk.jol</groupId>
                <artifactId>jol-core</artifactId>
                <version>0.10</version>
            </dependency>

基本使用

public static void main(String[] args) throws InterruptedException {
    
            Object o1 =new Object();
            System.out.println(ClassLayout.parseInstance(o1).toPrintable());
    
            Thread.sleep(5000);
            
            Object o =new Object();
            System.out.println(ClassLayout.parseInstance(o).toPrintable());
        }

输出结果

java.lang.Object object internals:
     OFFSET  SIZE   TYPE DESCRIPTION                               VALUE
          0     4        (object header)                           01 00 00 00 (00000001 00000000 00000000 00000000) (1)
          4     4        (object header)                           00 00 00 00 (00000000 00000000 00000000 00000000) (0)
          8     4        (object header)                           e5 01 00 f8 (11100101 00000001 00000000 11111000) (-134217243)
         12     4        (loss due to the next object alignment)
    Instance size: 16 bytes
    Space losses: 0 bytes internal + 4 bytes external = 4 bytes total
    
    java.lang.Object object internals:
     OFFSET  SIZE   TYPE DESCRIPTION                               VALUE
          0     4        (object header)                           05 00 00 00 (00000101 00000000 00000000 00000000) (5)
          4     4        (object header)                           00 00 00 00 (00000000 00000000 00000000 00000000) (0)
          8     4        (object header)                           e5 01 00 f8 (11100101 00000001 00000000 11111000) (-134217243)
         12     4        (loss due to the next object alignment)
    Instance size: 16 bytes
    Space losses: 0 bytes internal + 4 bytes external = 4 bytes total