Java中的单例

ゝ一纸荒年。 2021-09-30 04:10 158阅读 0赞

单例有饿汉式、懒汉式之分，这里通过几个简单的例子简单的说明一下，以供后续需要时参考~

--------------------

**1、饿汉式**

package com.oop.danli;
    /**
     * 单例：饿汉式
     * @author xzw
     *
     */
    public class SingleTon {
    	//1.构造器私有化
    	private SingleTon(){
    		//不能创建对象了
    	}
    	//2.自己创建对象
    	private static SingleTon instance = new SingleTon();
    	
    	//3.提供访问的接口
    	public static SingleTon getInstance(){
    		return instance;
    	}
    
    }

测试类：

package com.oop.danli;
    /**
     * 单例饿汉式测试类
     * @author xzw
     *
     */
    public class TestSingleTon {
    	
    	public static void main(String[] args) {
    		SingleTon instance1 = SingleTon.getInstance();
    		SingleTon instance2 = SingleTon.getInstance();
    		SingleTon instance3 = SingleTon.getInstance();
    		System.out.println(instance1 == instance2);
    		System.out.println(instance1 == instance3);
    		System.out.println(instance2 == instance3);
    	}
    
    }

测试结果：

true
    true
    true

**2、懒汉式**

package com.oop.danli;
    /**
     * 单例：懒汉式
     * @author xzw
     *
     */
    public class SingleTon2 {
    	//1.构造器私有化
    	private SingleTon2(){};
    	
    	//2.自己创建对象
    	private static SingleTon2 instance = null;
    	
    	//3.提供访问的接口
    	public static SingleTon2 getInstance(){
    		if (instance == null) {
    			instance = new SingleTon2();
    		}
    		return instance;
    	}
    
    }

测试类：

package com.oop.danli;
    /**
     * 单例懒汉式测试类
     * @author xzw
     *
     */
    public class TestSingleTon2 {
    	
    	public static void main(String[] args) {
    		SingleTon2 instance1 = SingleTon2.getInstance();
    		SingleTon2 instance2 = SingleTon2.getInstance();
    		SingleTon2 instance3 = SingleTon2.getInstance();
    		System.out.println(instance1 == instance2);
    		System.out.println(instance1 == instance3);
    		System.out.println(instance2 == instance3);
    	}
    
    }

测试结果：

true
    true
    true