Java的初始化块

1.类初始化块

// 类初始化块只执行一次
public class A {

    static {
        System.out.println("Hello World");
    }

    public static void main(String[] args) {
        A a = new A();
        A a1 = new A();
        A a2 = new A();
    }
}      

1.实例初始化块

// 实例初始化块每次实例化都会执行一次
public class B {

    {
        System.out.println("Hello World");
    }

    public static void main(String[] args) {
        B b = new B();
        B b1 = new B();
        B b2 = new B();
    }
}