暂停线程

暂停线程意味着线程还可以恢复运行

package resumeSuspend;

/**
 * Created by liping.sang on 2017/1/13 0013.
 */
public class MyThread extends  Thread{
    private long i=0;

    public void run(){
        while(true){
            i++;
        }
    }
    public long getI() {
        return i;
    }

    public void setI(long i) {
        this.i = i;
    }
}

package resumeSuspend;

import interruptedAndIsInterrupted.*;

/**
 * Created by Administrator on 2017/1/13 0013.
 */
public class Run {
    public static  void main(String [] args){
        try {
          MyThread thread =  new MyThread();
            thread.start();
            Thread.sleep(5000);
            //A
            thread.suspend();
            System.out.println("A"+System.currentTimeMillis()+" i="+thread.getI());
            Thread.sleep(5000);
            System.out.println("A"+System.currentTimeMillis()+" i="+thread.getI());
            //B
            thread.resume();
            Thread.sleep(5000);
            //C
            thread.suspend();
            System.out.println("B"+System.currentTimeMillis()+" i="+thread.getI());
            Thread.sleep(5000);
            System.out.println("B"+System.currentTimeMillis()+" i="+thread.getI());
        }catch (Exception e){

        }
    }
}

A1484293047430 i=3313762423
A1484293052430 i=3313762423
B1484293057430 i=6671460667
B1484293062430 i=6671460667

从执行结果来看，线程的确被暂停了，而且还可以恢复成运行的状态。

使用suspend和resume方法时，如果使用不当，极易造成公共的同步对象的独占，使得其他线程无法访问公共同步对象。

suspend和resume方法的缺点---不同步

使用suspend和resume方法时也容易出现因为线程的暂停二导致数据不同步的情况

看如下例子：

package suspend_resume_mosamevalue;

/**
 * Created by liping.sang on 2017/1/13 0013.
 */
public class MyObject {
    private String username = "1";
    private String password = "11";

    public  void setValue(String u,String p){
        this.username = u ;
        if(Thread.currentThread().getName().equals("a")){
            System.out.println("停止a线程");
            Thread.currentThread().suspend();
        }
        this.password = p;
    }
public void printUsernamePassword(){
    System.out.println(username+" "+password);
}

}

package suspend_resume_mosamevalue;

/**
 * Created by liping.sang on 2017/1/13 0013.
 */
public class Run {
    public static void main(String [] args) throws InterruptedException {
        final MyObject myobject = new MyObject();
        Thread thread1=new Thread(){
            public void run(){
                myobject.setValue("a","aa");
            }
        };
        thread1.setName("a");
        thread1.start();
        Thread.sleep(500);
        Thread thread2 = new Thread(){
            public void run(){
                myobject.printUsernamePassword();
            }
        };
        thread2.start();
    }
}

停止a线程
a 11

可以看出运行的结果出现了值不同步的情况。