11，多线程示例代码

实例1

package 多线程;
/*
 * 多窗口售票
 * 此程序为错误程序，每张票买了四次
 * */
class ticket extends Thread{
    private int ticket=100;
    public void run()
    {
        while(true)
        {
            if(ticket>0)
            {    
                System.out.println("sales："+ticket--);
            }
        }
    }
    
}
public class tick {
    public static void main(String[] args)
    {
        ticket t0=new ticket();
        ticket t1=new ticket();
        ticket t2=new ticket();
        ticket t3=new ticket();
        t0.start();    
        t1.start();
        t2.start();
        t3.start();
    }
    


}

示例代码2

解决多线程共享变量问题：声明实现runnable接口的类

解决打印0，-1，-2票：使用同步代码块

package 多线程;
/*
 * 多窗口售票
 * implements Runnable
 * */
class ticket implements  Runnable{
    private int ticket=100;
    public void run()
    {
        while(true)
        {
            synchronized (this) {
                if(ticket>0)
                {    try{Thread.sleep(10);}catch(Exception e){}
                    System.out.println(Thread.currentThread().getName()+"sales："+ticket--);
                }
            }
        }
    }
    
}
public class tick {
    public static void main(String[] args)
    {        
        ticket t=new ticket();
        Thread Th0=new Thread(t);
        Thread Th1=new Thread(t);
        Thread Th2=new Thread(t);
        Thread Th3=new Thread(t);
        Th0.start();    
        Th1.start();
        Th2.start();
        Th3.start();
    }
    


}

同步代码函数

package song.yan;

class Bank{
    private int sum;
    //同步代码块
    /*public void add(int n)
    {
        synchronized(this)
        {
            sum=sum+100;
            try{Thread.sleep(100);}catch(Exception e){}
            System.out.println("sum="+sum);        
        }        
    }*/
    //同步函数
    public synchronized void add(int n)
    {
        sum=sum+100;
        try{Thread.sleep(100);}catch(Exception e){}
        System.out.println("sum="+sum);        
        
    }
}
class Demos implements Runnable{
    private Bank b= new Bank();
    
    public void run()
    {
        for(int i=0;i<3;i++)
        {
            b.add(100);
        }
    }
}
public class tick{
    public static void main(String[] args) {
        Demos d=new Demos();
        Thread t1=new Thread(d);
        Thread t2= new Thread(d);
        t1.start();
        t2.start();
    }
    
}

//

package song.yan.com;
/*
 * 将同步设在run()
 * 将变成单线程问题
 * 
 * */

class Ticks implements Runnable{
    private int num=1000;
    
    public synchronized  void run()
    {
        while(true)
        {
            if(num>0)
            {
                System.out.println(Thread.currentThread().getName()+"num="+num--);
            }            
        }
        
    }
}
public class tick{
    public static void main(String[] args) {
        Ticks d=new Ticks();
        Thread t1=new Thread(d);
        Thread t2= new Thread(d);
        Thread t3=new Thread(d);
        Thread t4= new Thread(d);
        t1.start();
        t2.start();
        t3.start();
        t4.start();
    }
    
}

正确使用同步函数：将需要同步的部分单独写在synconized函数中，在run函数中调用

package song.yan.com;
/*
 * 将同步设在run()
 * 将变成单线程问题
 * 
 * */

class Ticks implements Runnable{
    private int num=2000;
    
    public   void run()
    {
        while(true)
        {
            show();            
        }
        
    }
    public synchronized void show()
    {
        if(num>0)
        {
            System.out.println(Thread.currentThread().getName()+"num="+num--);
        }
    }
}
public class tick{
    public static void main(String[] args) {
        Ticks d=new Ticks();
        Thread t1=new Thread(d);
        Thread t2= new Thread(d);
        Thread t3=new Thread(d);
        Thread t4= new Thread(d);
        t1.start();
        t2.start();
        t3.start();
        t4.start();
    }
    
}