jvm 初始化之 <cinit> , <init>

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java

public class T2{
static{
   System.out.println("-----.static---");
   }
   static T2 t2 = new T2();
   C t =new C();
   static String str = "ff"; 
   
   public T2(){System.out.println("-----...");}
  public static void main(String[] ages){
   String a = "hi";
    String s = "'"+a+"'";
    String ni= T2.str;
   }
}
class C{
 static{System.out.println("----cccccc  static-...");}
}

这个是test类。下面是字节码

{
static T2 t2;

C t;

static java.lang.String str;

public T2();<init>将相应的变量压入<init>方法中
  Code:
   Stack=3, Locals=1, Args_size=1
   0:   aload_0
   1:   invokespecial   #1; //Method java/lang/Object."<init>":()V
   4:   aload_0
   5:   new     #2; //class C
   8:   dup
   9:   invokespecial   #3; //Method C."<init>":()V
   12:  putfield        #4; //Field t:LC;
   15:  getstatic       #5; //Field java/lang/System.out:Ljava/io/PrintStream;
   18:  ldc     #6; //String -----...
   20:  invokevirtual   #7; //Method java/io/PrintStream.println:(Ljava/lang/Str
ing;)V
   23:  return
  LineNumberTable:
   line 11: 0
   line 8: 4
   line 11: 15


public static void main(java.lang.String[]);
  Code:
   Stack=2, Locals=4, Args_size=1
   0:   ldc     #8; //String hi
   2:   astore_1
   3:   new     #9; //class java/lang/StringBuilder
   6:   dup
   7:   invokespecial   #10; //Method java/lang/StringBuilder."<init>":()V
   10:  ldc     #11; //String '
   12:  invokevirtual   #12; //Method java/lang/StringBuilder.append:(Ljava/lang
/String;)Ljava/lang/StringBuilder;
   15:  aload_1
   16:  invokevirtual   #12; //Method java/lang/StringBuilder.append:(Ljava/lang
/String;)Ljava/lang/StringBuilder;
   19:  ldc     #11; //String '
   21:  invokevirtual   #12; //Method java/lang/StringBuilder.append:(Ljava/lang
/String;)Ljava/lang/StringBuilder;
   24:  invokevirtual   #13; //Method java/lang/StringBuilder.toString:()Ljava/l
ang/String;
   27:  astore_2
   28:  getstatic       #14; //Field str:Ljava/lang/String;
   31:  astore_3
   32:  return
  LineNumberTable:
   line 13: 0
   line 14: 3
   line 15: 28
   line 16: 32


static {};
  Code:
   Stack=2, Locals=0, Args_size=0
   0:   getstatic       #5; //Field java/lang/System.out:Ljava/io/PrintStream;
   3:   ldc     #15; //String -----.static---
   5:   invokevirtual   #7; //Method java/io/PrintStream.println:(Ljava/lang/Str
ing;)V
   8:   new     #16; //class T2
   11:  dup
   12:  invokespecial   #17; //Method "<init>":()V//调了T2<init>方法
   15:  putstatic       #18; //Field t2:LT2;
   18:  ldc     #19; //String ff
   20:  putstatic       #14; //Field str:Ljava/lang/String;
   23:  return
  LineNumberTable:
   line 5: 0
   line 7: 8
   line 9: 18


}

没注释static T2 t2 = new T2();//调了T2<init>方法
结果：-----.static---
----cccccc  static-...
-----...

{
C t;

static java.lang.String str;

public T2();<init>将相应的变量压入<init>方法中
  Code:
   Stack=3, Locals=1, Args_size=1
   0:   aload_0
   1:   invokespecial   #1; //Method java/lang/Object."<init>":()V
   4:   aload_0
   5:   new     #2; //class C
   8:   dup
   9:   invokespecial   #3; //Method C."<init>":()V
   12:  putfield        #4; //Field t:LC;
   15:  getstatic       #5; //Field java/lang/System.out:Ljava/io/PrintStream;
   18:  ldc     #6; //String -----...
   20:  invokevirtual   #7; //Method java/io/PrintStream.println:(Ljava/lang/Str
ing;)V
   23:  return
  LineNumberTable:
   line 11: 0
   line 8: 4
   line 11: 15


public static void main(java.lang.String[]);
  Code:
   Stack=2, Locals=4, Args_size=1
   0:   ldc     #8; //String hi
   2:   astore_1
   3:   new     #9; //class java/lang/StringBuilder
   6:   dup
   7:   invokespecial   #10; //Method java/lang/StringBuilder."<init>":()V
   10:  ldc     #11; //String '
   12:  invokevirtual   #12; //Method java/lang/StringBuilder.append:(Ljava/lang
/String;)Ljava/lang/StringBuilder;
   15:  aload_1
   16:  invokevirtual   #12; //Method java/lang/StringBuilder.append:(Ljava/lang
/String;)Ljava/lang/StringBuilder;
   19:  ldc     #11; //String '
   21:  invokevirtual   #12; //Method java/lang/StringBuilder.append:(Ljava/lang
/String;)Ljava/lang/StringBuilder;
   24:  invokevirtual   #13; //Method java/lang/StringBuilder.toString:()Ljava/l
ang/String;
   27:  astore_2
   28:  getstatic       #14; //Field str:Ljava/lang/String;
   31:  astore_3
   32:  return
  LineNumberTable:
   line 13: 0
   line 14: 3
   line 15: 28
   line 16: 32


static {};
  Code:
   Stack=2, Locals=0, Args_size=0
   0:   getstatic       #5; //Field java/lang/System.out:Ljava/io/PrintStream;
   3:   ldc     #15; //String -----.static---
   5:   invokevirtual   #7; //Method java/io/PrintStream.println:(Ljava/lang/Str
ing;)V
   8:   ldc     #16; //String ff
   10:  putstatic       #14; //Field str:Ljava/lang/String;
   13:  return
  LineNumberTable:
   line 5: 0
   line 9: 8


}


注释static T2 t2 = new T2(); 没有t2的<init>方法
结果：-----.static---

总结：当一个类初始化的时候，先调用<cinit>方法，如果在<cinit>方法中遇到<init>方法。则先调用完<init>方法。然后在继续执行<cinit>

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cinit init | jvm 初始化

2012-02-22 17:50
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