java 陷阱

猜猜输出什么？

class Test{

Test(){
do1();
}
public void do1(){
}
}
class Farther extends Test{


Integer   flag=new Integer(3);
Farther(){

System.out.println(flag);

}
public void do1()
{

System.out.println(flag);
}

public static void main(String args[]){



new Farther();
}
}
输出：
null
3
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interface Angry {  
    String greeting = "Grrrr!";  
    int angerLevel = Dog.getAngerLevel();  
}  
 
class Dog implements Angry {  
    public static final String greeting = "Wong, Wong, Wong!";  
      
    static {  
        System.out.println("Dog was initialized.");  
    }  
 
    public static int getAngerLevel() {  
        System.out.println("Angry was initialized.");  
        return 1;  
    }  
}  
 
class Main {  
    public static void main(String[] args) throws Exception {  
        testClassInit();  
    }  
 
    public static void testClassInit() throws Exception {  
 
        //passive use of Angry  
        System.out.println(Angry.greeting);  
 
        //passive use of Dog  
        System.out.println(Dog.greeting);  
    }  
} 
输出：
Grrrr!
Wong, Wong, Wong!

在 inside the jvm 书中，jvm对static final修饰的 变量，在其他类中只是用类名.Field，则只是简单 替换，而根本不需加载class。