线程安全--- synchronized

package com.Thread;

 

class W12306 implements Runnable{

       private boolean flag = true;

       private int num =10;

       @Override

       public void run() {

             while(flag ) {

                  test6();

            }

      }

      

       //线程不安全，锁定不正确，一般锁定对象

       public void test6() {

             if(num <=0) {

                   flag = false ;

                   return;

            }

             synchronized(this ) {

                   try {

                        Thread. sleep(500);//模拟网络延时，最后取到了0和-1

                  } catch (InterruptedException e) {

                        e.printStackTrace();

                  }

                  System. out.println(Thread.currentThread().getName() + "抢到了" + num--);

            }

 

      }

      

       //线程不安全，锁定资源不正确

       public void test5() {

             synchronized((Integer)num ) {

                   if(num <=0) {

                         flag = false ;

                         return;

                  }

                   try {

                        Thread. sleep(500);//模拟网络延时，最后取到了0和-1

                  } catch (InterruptedException e) {

                        e.printStackTrace();

                  }

                  System. out.println(Thread.currentThread().getName() + "抢到了" + num--);

            }

 

      }

 

      

       //线程不安全，锁定范围过小

       //a b c

       public void test4() {

             synchronized(this ) {

                   //b

                   if(num <=0) {

                         flag = false ;

                         return;

                  }

            }

             //b

             try {

                  Thread. sleep(500);//模拟网络延时，最后取到了0和-1

            } catch (InterruptedException e) {

                  e.printStackTrace();

            }

            System. out.println(Thread.currentThread().getName() + "抢到了" + num --);

             //a-->1

 

      }

 

      

       //线程安全，锁定方法块

       public void test3() {

             synchronized(this ) {

                   if(num <=0) {

                         flag = false ;

                         return;

                  }

                   try {

                        Thread. sleep(500);//模拟网络延时，最后取到了0和-1

                  } catch (InterruptedException e) {

                        e.printStackTrace();

                  }

                  System. out.println(Thread.currentThread().getName() + "抢到了" + num--);

            }

 

      }

 

      

       //线程安全，锁定方法

       public synchronized void test2() {

             if(num <=0) {

                   flag = false ;

                   return;

            }

             try {

                  Thread. sleep(500);//模拟网络延时，最后取到了0和-1

            } catch (InterruptedException e) {

                  e.printStackTrace();

            }

            System. out.println(Thread.currentThread().getName() + "抢到了" + num --);

 

      }

      

       //线程不安全

       public void test1() {

             if(num <0) {

                   flag = false ;

            }

             try {

                  Thread. sleep(500);//最后取到了0和-1

            } catch (InterruptedException e) {

                  e.printStackTrace();

            }

            System. out.println(Thread.currentThread().getName() + "抢到了" + num --);

 

      }

}

public class Synchronized_ {

       public static void main(String[] args) {

            W12306 w = new W12306();

            

            Thread t1 = new Thread(w, "甲" );

            Thread t2 = new Thread(w, "已" );

            Thread t3 = new Thread(w, "丁" );

            

            t2.start();

            t1.start();

            t3.start();

      }

}