Java线程

首先了解进程：是一个可执行程序放在计算机存储器的一个指令序列，它是一个动态执行过程

1线程定义

类似是进程的子程序

2线程创建

分为继承Thread类

线程的创建和启动下面的代码实现

package com.jiedada.thread;
//继承线程对象
 class MyThreads extends Thread{
     public MyThreads(String name)
     {
         super(name);
     }
     public void run()
     {
         for(int i=1;i<10;i++)
         {
             System.out.println(getName()+"这是第"+i+"次线程");
         }
     }
 }
public class ThreadOne {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        //创建线程对象
        MyThreads my1=new MyThreads("线程1");
        MyThreads my2=new MyThreads("线程2");
        my1.start();
        my2.start();
    }

}

和接口Runnable

为什么有类的线程却要再用runnalbe接口呢

1如果一个类继承了一个类，就不能继承Thread类了

2因为一些类只想使用run这一个方法

接口创建的类可以创建多个对象

接口类的定义，接口类的实列和start方法代码

package com.jiedada.thread;
//接口类的创建
class RunTest implements Runnable{

    @Override
    public void run() {
        // TODO Auto-generated method stub
        int i=1;
        while(i<10)
        {
            System.out.println(Thread.currentThread().getName()+"这是线程"+(i++));
        }
    }
    
}
public class Test {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        //接口类的调用start方法，接口类发生的情况
   RunTest r1=new RunTest();
   Thread thread=new Thread(r1);
   thread.start();
   RunTest r2=new RunTest();
   Thread t1=new Thread(r2);
   t1.start();
    }

}

3线程的状态和生命周期

1线程的状态分为

创建

可运行

正在运行

sleep请求，是一个Thread的静态方法，在在使用的时候需要使用try catch来捕获程序终端异常

可以是用于计时器，一段时间的数据更新

package com.jiedada.thread;
class SleepThread implements Runnable{

    @Override
    public void run() {
        // TODO Auto-generated method stub
        for(int i=0;i<15;i++)
        {
            System.out.println(Thread.currentThread().getName()+"这是线程"+i);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
    
}
public class SleepTest {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
   SleepThread s1=new SleepThread();
   Thread t=new Thread(s1);
   t.start();
    }

}

join请求，join是一个最终的方法等待调用该线程结束后才能执行；

package com.jiedada.thread;
class JoinT implements Runnable{

    @Override
    public void run() {
        // TODO Auto-generated method stub
        for(int i=0;i<15;i++)
        {
            System.out.println(Thread.currentThread().getName()+"这是一个线程"+i);
        }
    }
    
}
public class JoinThread {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        
        JoinT j=new JoinT();
        Thread t=new Thread(j);
        t.start();
        //这是一个join的方法里面可以放入时间参数
        try {
            t.join();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println("这是主线程");
    }

}

阻塞

终止

线程优先级

Java为线程优先级提供了1-10的优先级，超出范围会抛出异常

主线程优先级为5

package com.jiedada.thread;
class pThread extends Thread{
    String name;
    public pThread(String name) {
        this.name=name;
    }
    public void run()
    {
        for(int i=0;i<10;i++)
        {
            System.out.println(getName()+"这是线程"+i);
        }
    }
}
public class youxianji {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int sum=Thread.currentThread().getPriority();
        System.out.println(sum);
        pThread p=new pThread("线程1");
        pThread p1=new pThread("线程2");
        p.setPriority(10);
        p1.setPriority(1);
        p.start();
        p1.start();

    }

}

4线程调度

5同步与死锁

多线程运行的问题

1各个线程竞争CPU时间而获得运行时间

2各线程什么时候得到CPU时间，占用多久，是不可预测的

3一个正在运行着的线程在上面地方被暂停是不确定的

解决办法（同步）

用synchronized关键字来定义可以用于

1成员方法

2静态方法

3语句快

银行系统实列

bank类

package com.jiedada.bank;

public class Bank {
    private String count;
    private int money;
    public Bank()
    {
        
    }
    public Bank(String count, int money) {
        super();
        this.count = count;
        this.money = money;
    }
    public String getCount() {
        return count;
    }
    public void setCount(String count) {
        this.count = count;
    }
    public int getMoney() {
        return money;
    }
    public void setMoney(int money) {
        this.money = money;
    }
    @Override
    public String toString() {
        return "Bank [count=" + count + ", money=" + money + "]";
    }
    //存入钱
    public synchronized void SaveAccount()
    {
        int countmoney=this.money;
        countmoney+=200;
        try {
            Thread.sleep(10);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        setMoney(countmoney);
        System.out.println("存入后的钱为："+countmoney);
    }
    //取钱操作
    public synchronized void DrawAccount()
    {
        int countmoney=this.money;
        countmoney-=100;
        try {
            Thread.sleep(10);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        setMoney(countmoney);
        System.out.println("取出钱后为："+countmoney);
    }

}

save money类

package com.jiedada.bank;
//存钱
public class SaveMoney implements Runnable{
    Bank bank;
    public SaveMoney(Bank bank)
    {
        this.bank=bank;
    }
    @Override
    public void run() {
        // TODO Auto-generated method stub
        bank.SaveAccount();
    }
         

}

draw money类

package com.jiedada.bank;

public class DrawMoney implements Runnable {

    Bank bank;

    public DrawMoney(Bank bank)
    {
        this.bank=bank;
    }

    @Override
    public void run() {
        // TODO Auto-generated method stub
        bank.DrawAccount();
    }
   
}

test类

package com.jiedada.bank;

public class Test {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        //创建账户
        Bank huang=new Bank("huangdada",1000);
        //创建线程
        SaveMoney s=new SaveMoney(huang);
        Thread t1=new Thread(s);
        DrawMoney d=new DrawMoney(huang);
        Thread t2=new Thread(d);
        t1.start();
        t2.start();
        try {
            t1.join();
            t2.join();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
        System.out.println(huang);

    }

}

 问腿

当银行中的钱不够时，我们就不能取出钱了。

举例生产者和消费者问题

qeuqe类

package com.jiedada.prodacanduse;

public class Qeuqe {
    private int n;
    boolean flag=false;
    public synchronized int get()
    {
        if(!flag)
        {
            try {
                wait();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        System.out.println("取出的："+n);
        flag=false;
        notifyAll();
        return n;
    }
    public synchronized int set(int n)
    {
        if(flag)
        {
            try {
                wait();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        System.out.println("存入的："+n);
        flag=true;
        notifyAll();
        return this.n=n;
        
    }
}

prodtion类

package com.jiedada.prodacanduse;

public class Prodction implements Runnable{
    Qeuqe qeuqe;
    public Prodction(Qeuqe qeuqe)
    {
        this.qeuqe=qeuqe;
    }

    @Override
    public void run() {
        // TODO Auto-generated method stub
        int i=0;
        while(true)
        {
        qeuqe.set(i++);
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        }
    }

}

package com.jiedada.prodacanduse;

public class User implements Runnable{
      Qeuqe queqe;
      
      public User(Qeuqe qeuqe)
      {
          this.queqe=qeuqe;
      }

    @Override
    public void run() {
        // TODO Auto-generated method stub
        while(true)
        {
            queqe.get();
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        
    }

}

test类

package com.jiedada.prodacanduse;

public class Test {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Qeuqe q1=new Qeuqe();
        new Thread(new Prodction(q1)).start();
        new Thread(new User(q1)).start();

    }

}