设计模式

饿汉式： 一开始就已经创建好了`King`的对象，随时可供调用/获取public class King 
public class King {
		
    private static King king = new King();

    private King() {
    }

    public static King getInstance() {
        return king;
    }

}

懒汉式： 它的特点是“不到逼不得已的时候，并不会创建对象”
public class King {

    private static King king = null;

    private static final Object lock = new Object();

    private King() {
    }

    public static King getInstance() {
        if (king == null) {
            sychronized (lock) {
                if (king == null) {
                    king = new King();
                    }
                }
            }
        return king;
    }

}