线程

线程的概念
      一个程序中的方法有几条执行路径, 就有几个线程

线程的创建:
     两种方式:
          1, 继承Thread类
                      class TestThread extends Thread {......}
          2, 实现Runnable接口, 然后作为参数传入到Thread类的构造方法中
                      class TestThread implements Runnable {......}

线程的启动:
          调用线程类中的start()方法, 不能直接调用run()方法, 直接调用run()方法那叫方法调用, 不是启动线程

线程常用方法
      isAlive()
              判断线程是否还活着, 调用start()之前和终止之后都是死的, 其他的都是活的
      interrupt()
              停止线程
      getPriority()

      setPriority()
            设置优先级, 优先级的概念: 谁的优先级高, 谁执行的时间就多
      Thread里面的默认优先级:
              Thread.MIN_PRIORITY = 1
              Thread.MAX_PRIORITY = 10
              Thread.NORM_PRIORITY = 5
              Thread.sleep(long millions)
                             将程序暂停一会
      join()
          合并线程
     yield()---礼让
            让出CPU执行其他线程
     wait()---简单了解
     notify()---简单了解
     notifyAll()---简单了解

public class TextThread {
    public static void main(String[] args){
        MyTherad mt = new MyTherad();
        // mt.start();
        Thread t = new Thread(mt);
        System.out.println("调用start之前："+t.isAlive());
        t.start();
        System.out.println("调用start之后："+t.isAlive());
        for(int i=0;i<50;i++){
            System.out.println("main"+i);
        }
    }
    
    public static void m(){
        for(int i=0;i<50;i++){
            System.out.println("===="+i);
        }
    }
}

class MyTherad implements Runnable{   //实现接口
    @Override
    public void run() {
        for(int i=0;i<50;i++){
            System.out.println("===="+i);
        }
    }
}

/*class MyThread extends Thread{

    @Override
    public void run() {
        for(int i=0;i<50;i++){
            System.out.println("===="+i);
        }
    }
    
} */

import java.util.Date;

public class TextThread2 {
    public static void main(String[] args){
        MyNewThread mt = new MyNewThread();
        Thread t = new Thread(mt);
        t.start();
/*        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
*/
        //t.interrupt();
        //t.stop();
        //终止进程将run方法结束进程就结束了
        //MyNewThread.flag= false;
    } 
}
class MyNewThread implements Runnable{

    @Override
    public void run() {
        while(true){
            System.out.println(new Date());
            try{
            Thread.sleep(1000);
           } catch(Exception e) {
               System.out.println("线程终止");
               System.out.println(e.getMessage());
               
           }
        }
    }    
}

线程同步

银行取钱例题

public class Text {
    public int money =3000;
    public void getMoney(String name,int mon){
        synchronized(this){
            if(money>mon && money>0){
                money -= mon;
                System.out.println("姓名"+name);
                System.out.println("取款"+mon);
                System.out.println("剩余金额："+money);
            }else{
                System.out.println("姓名"+name);
                System.out.println("余额不足");
                System.out.println("剩余金额"+money);
            }
        }
    }
}

public class Text2 {
    public static void main(String[] args){
        MyTherad at = new MyTherad();
        
        Thread t1 = new Thread(at);
        Thread t2 = new Thread(at);
        
        t2.setName("刘毅");
        t1.setName("蒋桥");
        
        t1.start();
        t2.start();
    }
}
class MyTherad implements Runnable{
    public Text bank = new Text();
    @Override
    public void run() {
        bank.getMoney(Thread.currentThread().getName(),2000);
        
    }
    
} 

死锁例题

public class Text3{
    public static void main(String[] args){
         Text3 d1 = new Text3();
         Text3 d2 = new Text3();
         
         d1.flag=1;
         d2.flag=2;
         
         Thread t1 = new Thread();
         Thread t2 = new Thread();
         
         t1.start();
         t2.start();
     }
    public static Object obj1 = new Object();
    public static Object obj2 = new Object(); 
    
    public int flag;
    
    public void run() {
        if (flag == 1) {
            System.out.println("这是第" + flag + "个线程");
            synchronized (obj1) {
                try {
                    Thread.sleep(500);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                synchronized (obj2) {
                    System.out.println("第" + flag + "个线程结束");
                }
            }
        }
        
        if (flag == 2) {
            System.out.println("这是第" + flag + "个线程");
            synchronized (obj2) {
                try {
                    Thread.sleep(500);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                synchronized (obj1) {
                    System.out.println("第" + flag + "个线程结束");
                }
            }
        }

    }
}