三种设计模式的实现

1.消费者生产者模式

import java.util.PriorityQueue;
import java.util.Queue;

public class ProducerAndConsumer {
    private final int capacity = 100;
    Queue<Integer> que = new PriorityQueue<>(capacity);
    public static void main(String[] args) {
        ProducerAndConsumer p = new ProducerAndConsumer();
        Thread t1 = new Thread(p.new Producer());
        Thread t2 = new Thread(p.new Consumer());
        t1.start();
        t2.start();
    }
    class Producer implements Runnable{        
        @Override
        public void run() {
            // TODO Auto-generated method stub
            while (true) {
                synchronized (que) {
                    while (que.size() == capacity) {
                        try {
                            wait();
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                            notify();
                        }
                    }
                    que.offer(1);
                    notify();
                }                
            }            
        }
    }
    class Consumer implements Runnable{
        public void run() {
            while (true) {
                synchronized (que) {
                    while (que.size() == 0) {
                        try {
                            wait();
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                            notify();
                        }
                    }
                    que.poll();
                    notify();
                }                
            }            
        }        
    }    
}

2.单例模式

需要注意构造方法需要设置为private，防止类在类外被实例化，获得类实例的唯一方法是通过getInstance();然后就是多线程加锁的处理。

package 单例模式;

/*饿汉式*/
/*
public class Singleton {
    private static final Singleton sg = new Singleton();
    private Singleton() {
        
    }
    public static Singleton getInstance() {
        return sg;
    }
}
*/
/*懒汉式*/
//线程不安全，多线程会出现多个实例
/*
public class Singleton {
    private static Singleton sg;
    private Singleton() {
        
    }
    public static Singleton getInstance() {
        if (sg == null) {
            return new Singleton();
        }        
        return sg;
    }
}
*/
//多线程懒汉模式
public class Singleton {
    private volatile static Singleton sg;
    private Singleton() {
        
    }
    public static Singleton getInstance() {
        if (sg == null) {
            synchronized (sg.getClass()) {
                if (sg == null) {//不加这一行还是会造成线程不安全
                    return new Singleton();
                }
            }            
        }        
        return sg;
    }
}

3.工厂模式

http://blog.csdn.net/jason0539/article/details/23020989

http://blog.csdn.net/jason0539/article/details/44976775