java中＂Static块＂是怎么回事,怎么用的,有什么意义

6.Static块 　

Static块：该类的任何方法被首次触碰到时(马克-to-win: when you touch Test的main方法时)，Static块被运行。可以在里面初始化你的static变量，不能访问实例变量。在所有静态变量初始化之后运行，见例子。

 

class Test1{
    static {
        System.out.println("Static block Test1 initialized.");
    }
}
public class Test {
    /*下面两句话是在静态块儿之前执行，所以它的值，被静态块儿里面赋的值所覆盖掉。马克-to-win， the following two statements are before the execution of the static block.*/
    static int a = 3;
    static int b;
    int c;

    static void cal(int x) {
        System.out.println("x = " + x);
        System.out.println("a = " + a);
        System.out.println("b = " + b);
    }

    // 静态块儿Static block
    static {
        // c=9; 是错误的，will cause an error.
        System.out.println("Static block initialized.");
        a = 9;
        b = a * 4;
        System.out.println("a = " + a);
        System.out.println("b = " + b);    }

    public static void main(String args[]) {
        System.out.println("in main");
/* main and cal 都是静态块儿，所以可以这样调用，here main and cal is on the same class and same level, so can use in this way.*/
        cal(42);
        new Test1();
    }
}

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