元空间、堆、线程在内存中的联系

短命女 2021-10-19 06:58 353阅读 0赞

下面分析一下元空间、堆、线程在内存中的联系

以下面代码为例

public class HelloWorld {
    	
    	private String name;
    	
    	public void sayHello() {
    		System.out.println(name);
    	}
    	
    	public void setName(String name) {
    		this.name = name;
    	}
    	
    	public static void main(String[] args) {
    		int a = 1;
    		HelloWorld hw = new HelloWorld();
    		hw.setName("test");
    		hw.sayHello();
    	}
    }

让我们来反编译下HelloWorld.class文件

C:\Users\Administrator\Desktop>javac HelloWorld.java
    
    C:\Users\Administrator\Desktop>javap -verbose HelloWorld
    Classfile /C:/Users/Administrator/Desktop/HelloWorld.class
      Last modified 2019-8-18; size 635 bytes
      MD5 checksum cf6b1e8b7a93a33de46deafdde7503c9
      Compiled from "HelloWorld.java"
    public class HelloWorld
      minor version: 0
      major version: 52
      flags: ACC_PUBLIC, ACC_SUPER
    Constant pool:
       #1 = Methodref          #10.#24        // java/lang/Object."<init>":()V
       #2 = Fieldref           #25.#26        // java/lang/System.out:Ljava/io/PrintStream;
       #3 = Fieldref           #5.#27         // HelloWorld.name:Ljava/lang/String;
       #4 = Methodref          #28.#29        // java/io/PrintStream.println:(Ljava/lang/String;)V
       #5 = Class              #30            // HelloWorld
       #6 = Methodref          #5.#24         // HelloWorld."<init>":()V
       #7 = String             #31            // haha
       #8 = Methodref          #5.#32         // HelloWorld.setName:(Ljava/lang/String;)V
       #9 = Methodref          #5.#33         // HelloWorld.sayHello:()V
      #10 = Class              #34            // java/lang/Object
      #11 = Utf8               name
      #12 = Utf8               Ljava/lang/String;
      #13 = Utf8               <init>
      #14 = Utf8               ()V
      #15 = Utf8               Code
      #16 = Utf8               LineNumberTable
      #17 = Utf8               sayHello
      #18 = Utf8               setName
      #19 = Utf8               (Ljava/lang/String;)V
      #20 = Utf8               main
      #21 = Utf8               ([Ljava/lang/String;)V
      #22 = Utf8               SourceFile
      #23 = Utf8               HelloWorld.java
      #24 = NameAndType        #13:#14        // "<init>":()V
      #25 = Class              #35            // java/lang/System
      #26 = NameAndType        #36:#37        // out:Ljava/io/PrintStream;
      #27 = NameAndType        #11:#12        // name:Ljava/lang/String;
      #28 = Class              #38            // java/io/PrintStream
      #29 = NameAndType        #39:#19        // println:(Ljava/lang/String;)V
      #30 = Utf8               HelloWorld
      #31 = Utf8               haha
      #32 = NameAndType        #18:#19        // setName:(Ljava/lang/String;)V
      #33 = NameAndType        #17:#14        // sayHello:()V
      #34 = Utf8               java/lang/Object
      #35 = Utf8               java/lang/System
      #36 = Utf8               out
      #37 = Utf8               Ljava/io/PrintStream;
      #38 = Utf8               java/io/PrintStream
      #39 = Utf8               println
    {
      public HelloWorld();
        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 1: 0
    
      public void sayHello();
        descriptor: ()V
        flags: ACC_PUBLIC
        Code:
          stack=2, locals=1, args_size=1
             0: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream
             3: aload_0
             4: getfield      #3                  // Field name:Ljava/lang/String;
             7: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/
            10: return
          LineNumberTable:
            line 6: 0
            line 7: 10
    
      public void setName(java.lang.String);
        descriptor: (Ljava/lang/String;)V
        flags: ACC_PUBLIC
        Code:
          stack=2, locals=2, args_size=2
             0: aload_0
             1: aload_1
             2: putfield      #3                  // Field name:Ljava/lang/String;
             5: return
          LineNumberTable:
            line 10: 0
            line 11: 5
    
      public static void main(java.lang.String[]);
        descriptor: ([Ljava/lang/String;)V
        flags: ACC_PUBLIC, ACC_STATIC
        Code:
          stack=2, locals=3, args_size=1
             0: iconst_1
             1: istore_1
             2: new           #5                  // class HelloWorld
             5: dup
             6: invokespecial #6                  // Method "<init>":()V
             9: astore_2
            10: aload_2
            11: ldc           #7                  // String haha
            13: invokevirtual #8                  // Method setName:(Ljava/lang/String;)V
            16: aload_2
            17: invokevirtual #9                  // Method sayHello:()V
            20: return
          LineNumberTable:
            line 14: 0
            line 15: 2
            line 16: 10
            line 17: 16
            line 18: 20
    }
    SourceFile: "HelloWorld.java"

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