多线程

多线程的第一种写法:
继承Thread类

package com.nbchina;

class Demo extends Thread{
	
	private String demoName;
	Demo(String demoName) {
		this.demoName=demoName;
	}

	public void run(){
		for(int x=0;x<60;x++)
			System.out.println(demoName+" extends Thread demo run == "+x);
	}
}


public class ThreadDemo {

	public static void main(String[] args) {
		Demo demoThread1 = new Demo("Thread1");
		Demo demoThread2 = new Demo("Thread2");
		demoThread1.start();
		demoThread2.start();
		for(int x=0;x<60;x++)
			System.out.println("main Thread++"+x);
	}

}

多线程的第二种写法:
继承接口Runnable

package com.nbchina;

class TicketDemo implements Runnable{
	private int tick=10000;
	
	public void run(){
		while(true){
			if(tick>0){
				System.out.println(Thread.currentThread().getName()+" TicketDemo sale : "+tick--);
			}
		}
	}
}


public class ThreadDemo {

	public static void main(String[] args) {
		TicketDemo t = new TicketDemo();
		Thread t1 = new Thread(t);
		Thread t2 = new Thread(t);
		t1.start();
		t2.start();

		

	}

}

通过synchronized代码酷块解决安全问题.共享变量tick,通过synchronized锁住执行代码块.

package com.nbchina;

class TicketDemo implements Runnable{
	private int tick=10000;
	
	public void run(){
		while(true){
			synchronized(TicketDemo.class){
				if(tick>0){
					System.out.println(Thread.currentThread().getName()+" TicketDemo sale : "+tick--);
				}
			}
		}
	}
}


public class ThreadDemo2 {

	public static void main(String[] args) {
		TicketDemo t = new TicketDemo();
		Thread t1 = new Thread(t);
		Thread t2 = new Thread(t);
		t1.start();
		t2.start();

		

	}

}

通过自定义方法,附加synchronized,来解决共享变量安全问题

package com.nbchina;

class TicketDemo implements Runnable{
	private static int tick=10000;
	public void run(){
		while(true){
			show();
		}
	}
	public static synchronized void show(){
		if(tick>0){
			System.out.println(Thread.currentThread().getName()+" TicketDemo2 sale : "+tick--);
		}
	}
}




public class ThreadDemo2 {
	public static void main(String[] args) {
		TicketDemo t = new TicketDemo();
		Thread t1 = new Thread(t);
		Thread t2 = new Thread(t);
		t1.start();
		t2.start();
	}

}

设计模式单例模式

class Single{//懒汉式
	private static final Single s=new Single();
	private Single(){}
	public static Single getInstance(){
		return s;
	}

}

class Single{//恶汉式
	private static Single s=null;
	private Single(){}
	public static Single getInstance(){
		if(s==null){
			synchronized(Single.class){
				if(s==null){
					s=new Single();
				}
			}
		}
		return s;
	}
}

public class SingletonTest {
	public static void main(String[] arges){
		Single single = Single.getInstance();
		Single single2 = Single.getInstance();
		System.out.print(singleton2==singleton);
	}
}

一个资源,一个生产者一个索取者,利用synchronized函数块,以及notifyAll()、Runnable互斥。程序缺点是notifyAll()需要全部唤醒我方和对方所有等待进程。所以改进在jdk1.5。使用显示锁lock

package com.nbchina;


class Resource{
	private String name;
	private int count = 1;
	private boolean flag = false;
	
	public synchronized void set(String name){
		while(flag)//注意：必须while 判断，不能if 。因为唤醒所有的等待进程，若当初等待进程再判断if之后等待，那么我方唤醒之后，我方等待的资源可能立即抢占互斥对方等待进程cpu的执行。因为不需要循环判断，那么就直接执行下面。
			try{this.wait();}catch(Exception e){}
		this.name = name+":"+count++;
		
		System.out.println(Thread.currentThread().getName()+"[生产者]"+this.name);
		flag = true;
		this.notifyAll();//唤醒对方以及我方线程
	}
	
	public synchronized void out(){
		while(!flag)
			try{this.wait();}catch(Exception e){}
		
		System.out.println(Thread.currentThread().getName()+"[消费者]"+this.name);
		flag = false;
		this.notifyAll();
	}
}

class Producer implements Runnable{
	private Resource res;
	Producer(Resource res){
		this.res=res;
	}
	public void run(){
		while(true){
			res.set("-商品");
		}
	}
}

class Consumer implements Runnable{
	private Resource res;
	Consumer(Resource res){
		this.res=res;
	}
	public void run(){
		while(true){
			res.out();
		}
	}
}

public class ThreadDemo4 {

	public static void main(String[] args) {
		Resource r = new Resource();
		Producer pro = new Producer(r);
		Consumer con = new Consumer(r);
		
		Thread t1 = new Thread(pro);
		Thread t2 = new Thread(con);
		
		t1.start();
		t2.start();
	}

}

互斥使用资源，利用jdk1.5中的lock解决方案。

package com.nbchina;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * jdk1.5提供了多线程升级解决方案.将同步Synchronized替换成Lock操作.
 * 将Object中的wait,notify notifyAll换成Condition对象.
 */
class Resource{
	private String name;
	private int count = 1;
	private boolean flag = false;
	
	private Lock lock =new ReentrantLock();
	private Condition condition_pro = lock.newCondition();
	private Condition condition_con = lock.newCondition();
	
	public void set(String name) throws InterruptedException{
		lock.lock();
		try{
			while(flag)
				condition_pro.await();
			this.name = name+":"+count++;
			
			System.out.println(Thread.currentThread().getName()+"[生产者]"+this.name);
			flag = true;
			condition_con.signal();	
		}finally{
			lock.unlock();
		}

	}
	
	public void out() throws InterruptedException{
		lock.lock();
		try{
			while(!flag)
				condition_con.await();
			System.out.println(Thread.currentThread().getName()+"[消费者]"+this.name);
			flag = false;
			condition_pro.signal();	
		}finally{
			lock.unlock();
		}

	}
}

class Producer implements Runnable{
	private Resource res;
	Producer(Resource res){
		this.res=res;
	}
	public void run(){
		while(true){
			try {
				res.set("-商品");
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}
}

class Consumer implements Runnable{
	private Resource res;
	Consumer(Resource res){
		this.res=res;
	}
	public void run(){
		while(true){
			try {
				res.out();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}
}

public class ThreadDemo5 {

	public static void main(String[] args) {
		Resource r = new Resource();
		Producer pro = new Producer(r);
		Consumer con = new Consumer(r);
		
		Thread t1 = new Thread(pro);
		Thread t2 = new Thread(con);
		
		t1.start();
		t2.start();
	}

}