class HelloA {

    public HelloA() {

        System.out.println("HelloA");

    }

    { System.out.println("I'm A class"); }

    static { System.out.println("static A"); }

}

public class HelloB extends HelloA {

    public HelloB() {

        System.out.println("HelloB");

    }

    { System.out.println("I'm B class"); }

    static { System.out.println("static B"); }

    public static void main(String[] args) {

        System.out.println("-------main start-------");

        new HelloB();

        new HelloB();

        System.out.println("-------main end-------");

    }

}

public class HelloA {

    public HelloA() {

        System.out.println("HelloA");

    }

    {

        System.out.println("I'm A class");

    }

    static {

        System.out.println("static A");

    }

}

public class HelloB extends HelloA {

    private HelloB() {

        System.out.println("HelloB");

    }

    public static HelloB getInstance(){

        return TestHolder.instance;

    }

    {

        System.out.println("I'm B class");

    }

    static {

        System.out.println("static B");

    }

    public static void main(String[] args) {

        System.out.println("-------main start-------");

//        new Test();

//        new Test();

        HelloB.getInstance();

        HelloB.getInstance();

        System.out.println("-------main end-------");

    }

    public static class TestHolder{

        static {

            System.out.println("static TestHolder");

        }

        {

            System.out.println(" TestHolder.................");

        }

        public static HelloB instance =new HelloB();

    }

}