2019.4.11

单例模式：

　　1、懒汉式

package com.danli;
/**
 * 懒汉式
 * @author Administrator
 *
 */
public class User {
	private static User user = null;
	
	private User() {}
	
	synchronized public static User getUser() {
		if(user==null) {
			user = new User();
		}
		return user;
	}
}

　　

package com.danli;
/**
 * 线程 类
 * @author Administrator
 *
 */
public class MyThread implements Runnable{

	@Override
	public void run() {
		for(int i = 0;i<10;i++) {
			User user = User.getUser();
			System.out.println(user);
		}
	}
	
}

　　

package com.danli;
/**
 * 测试类
 * @author Administrator
 *
 */
public class Main {
	public static void main(String[] args) {
		MyThread mt = new MyThread();
		Thread t1 = new Thread(mt);
		Thread t2 = new Thread(mt);
		Thread t3 = new Thread(mt);
		Thread t4 = new Thread(mt);
		
		t1.start();
		t2.start();
		t3.start();
		t4.start();
		
	}
}

　　测试示例：

　　2、饿汉式

package com.danli;
/**
 * 饿汉式
 * @author Administrator
 *
 */
public class User2 {
	private static final User2 user = new User2();
	
	private User2() {}
	
	public static User2 getUser() {
		return user;
	}
}

　　

package com.danli;
/**
 * 线程 类
 * @author Administrator
 *
 */
public class MyThread implements Runnable{

	@Override
	public void run() {
		for(int i = 0;i<10;i++) {
			User2 user = User2.getUser();
			System.out.println(user);
		}
	}
}

　　

package com.danli;
/**
 * 测试类
 * @author Administrator
 *
 */
public class Main {
	public static void main(String[] args) {
		MyThread mt = new MyThread();
		Thread t1 = new Thread(mt);
		Thread t2 = new Thread(mt);
		Thread t3 = new Thread(mt);
		Thread t4 = new Thread(mt);
		
		t1.start();
		t2.start();
		t3.start();
		t4.start();
		
	}
}

　　结果示例：

　　3、枚举单例：

package com.enumsingle;
/**
 * 枚举单例
 * @author Administrator
 *
 */
public class Single{
	//私有化无参构造
    private Single(){}
    //创建静态获取实例方法getInstance()
    public static Single getInstance(){
        return EnumSingle.INSTANCE.getInstance();
    }
    
    private static enum EnumSingle{
        INSTANCE;
        //私有化实例对象
        private Single single;
        //通过枚举类无参构造方法创建对象
        private EnumSingle(){
            single = new Single();
        }
        
        public Single getInstance(){
            return single;
        }
    }
}

　　

package com.enumsingle;
/**
 * 线程 类
 * @author Administrator
 *
 */
public class MyThread implements Runnable{

	@Override
	public void run() {
		for(int i = 0;i<10;i++) {
			Single es = Single.getInstance();
			System.out.println(es);
		}
	}
}

package com.enumsingle;
/**
 * 测试类
 * @author Administrator
 *
 */
public class Main {
	public static void main(String[] args) {
		MyThread mt = new MyThread();
		Thread t1 = new Thread(mt);
		Thread t2 = new Thread(mt);
		Thread t3 = new Thread(mt);
		Thread t4 = new Thread(mt);
		
		t1.start();
		t2.start();
		t3.start();
		t4.start();
		
	}
}

　　结果示例