几种单例模式

1.饿汉单例模式

public class Single {
	
	public static final Single instance = new Single();
	public static Single getInstance(){
		return instance;
	}
	private Single(){
		//Single诞生时要做的事情
	}
	public void oneMethod() {
		System.out.println("I am oneMethod!");
	}
}

2.懒汉单例模式

public class Single {
	
	public static Single instance = null;
	
	public static Single getInstance(){
		if(instance == null){
			instance = new Single();
		}
		return instance;
	}
	private Single(){
		//Single诞生时要做的事情
	}
	public void oneMethod() {
		System.out.println("I am oneMethod!");
	}
}

3.静态内部类

public class Single {
	
	private static class SigletonHolder {
		private static Single instance = new Single();
	}
	public static final Single getInstance() {
		return SigletonHolder.instance;
	}
	private Single() {
		//MaYun诞生要做的事情
	}
	public void oneMethod() {
		System.out.println("I am oneMethod!");
	}
}

4.枚举单例模式

public enum Single {
	
	NumberZero(0),
    NumberOne(1),
    NumberTwo(2),
    NumberThree(3);

    private final int value;

    Single(int value) {
        this.value = value;
    }

    public int getValue() {
        return value;
    }
}