停止与暂停线程

停止线程：

interrupt()方法停止线程

this.interrupted() 测试当前的线程是否处于中断状态，并会将状态标志清除为false。

this.isInterrupted() 测试thread线程是否处于中断状态，不会去改变状态。
在沉睡中停止：

在sleep状态下停止线程：结果是会进入catch语句，并且会将停止状态置为false

public class MyThread extends Thread{
    @Override
    public void run() {
        super.run();
        try {
            System.out.println("run begin");
            Thread.sleep(200000);
            System.out.println("run end");
        } catch (InterruptedException e) {
            System.out.println("在沉睡中被停止，进入catch"+this.isInterrupted());
            e.printStackTrace();
        }
    }
}
public class Run {
    public static void main(String[] args) {
        try {
            MyThread thread=new MyThread();
            thread.start();
            Thread.sleep(200);
            thread.interrupt();
        } catch (InterruptedException e) {
            System.out.println("main catch");
            e.printStackTrace();
        }
        System.out.println("end");
    }
}

另外一种是先停止，再遇到sleep，进入到catch

public class MyThread1 extends Thread {
    @Override
    public void run() {
        super.run();
        try {
            for(int i=0;i<100000;i++) {
                System.out.println("i="+(i+1));
            }
            System.out.println("run begin");
            Thread.sleep(200000);
            System.out.println("run end");
        } catch (Exception e) {
            System.out.println("先停止，再遇到sleep 进入catch");
            e.printStackTrace();
        }
    }
}
public class Run1 {
    public static void main(String[] args) {
        MyThread1 thread1=new MyThread1();
        thread1.start();
        thread1.interrupt();
        System.out.println("end!");
    }
}

stop 暴力停止线程，可以停止，但是可能会造成一些不可预期的后果，已经废止，不建议使用 后果是：1，一些清理工作没有完成  2，可能会对一些加锁的对象进行解锁，造成数据的不同步

stop 方法会进入threadDath异常

public class MyThread extends Thread{
    private int i=0;    
    @Override
    public void run() {
        try {
            while (true) {
                i++;
                System.out.println("i="+i);
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
public class Run {
    public static void main(String[] args) {
        try {
            MyThread thread=new MyThread();
            thread.start();
            Thread.sleep(8000);
            thread.stop();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

调用stop方法停止线程，对加锁的对象进行了解锁，造成数据不同步的例子

public class SynchronizedObject {
    private String userName="a";
    private String password="aa";    
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getUserName() {
        return userName;
    }    
    public void setUseName(String userName) {
        this.userName=userName;
    }
    // 这个方法加锁后，本来userName和password要么都被赋予新值，要么都未被赋值
    synchronized public void printString(String userName,String password) {
        try {
            this.userName=userName;
            Thread.sleep(100000);
            this.password=password;
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

public class MyThread extends Thread{
    private SynchronizedObject object;
    public MyThread(SynchronizedObject object) {
        super();
        this.object=object;
    }
    @Override
    public void run() {
        object.printString("b", "bb");
    }
}

public class Run {
    public static void main(String[] args) {
        try {
            SynchronizedObject object=new SynchronizedObject();
            MyThread thread=new MyThread(object);
            thread.start();
            thread.sleep(500);
            thread.stop();//在调用stop方法后将锁给解锁了，造成数据不一致
            System.out.println(object.getUserName()+" "+object.getPassword());//前者被赋值了，而后者没有 结果是 b aa
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

 采用interupt方法和return来停止线程

public class MyThread extends Thread{
    @Override
    public void run() {
        while (true) {
            if(this.isInterrupted()) {//检查中断状态
                System.out.println("停止了");
                return; //若中断状态为true则结束线程，返回达到线程停止的目的
            }
            System.out.println("timer="+System.currentTimeMillis());
        }
    }
}
public class Run {
    public static void main(String[] args){
        try {
            MyThread thread=new MyThread();        
            thread.start();
            Thread.sleep(200);
            thread.interrupt();//调用中断线程的方法
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

暂停线程：

采用suspend和resume方法可以暂停线程和使线程重新恢复运行

public class MyThread extends Thread{
    private long i=0;
    public long getI() {
        return i;
    }
    public void setI(long i) {
        this.i = i;
    }
    @Override
    public void run() {
        while (true) {
            i++;
        }
    }
}
public class Run {
    public static void main(String[] args) {
        try {
            MyThread thread =new MyThread();
            thread.start();
            Thread.sleep(5000);
            
            thread.suspend();//暂停线程
            System.out.println("A="+System.currentTimeMillis()+"i="+thread.getI());
            Thread.sleep(5000);
            System.out.println("A="+System.currentTimeMillis()+"i="+thread.getI());
            
            thread.resume();//使线程重新恢复运行
            Thread.sleep(5000);
            System.out.println("B="+System.currentTimeMillis()+"i="+thread.getI());
            Thread.sleep(5000);
            System.out.println("B="+System.currentTimeMillis()+"i="+thread.getI());
            
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
          /*A=1550371225618i=3775194690
            A=1550371230629i=3775194690
            B=1550371235630i=7719710287
            B=1550371240642i=11697485852*/
}

 使用suspend方法可能会造成公共同步对象的强占，而其他线程无法使用。

public class SynchrinizedObject {
    synchronized public void printString() {
        System.out.println("begin");
        if(Thread.currentThread().getName().equals("a")) {
            System.out.println("a线程永远suspend 了");
            Thread.currentThread().suspend();
        }
        System.out.println("end");
    }
}
public class Run {
    public static void main(String[] args) {
        try {
            final SynchrinizedObject object=new SynchrinizedObject();
            Thread thread=new Thread() {
                @Override
                public void run() {
                    object.printString();
                }
            };
            thread.setName("a");
            thread.start();
            thread.sleep(1000);
        
            Thread thread2=new Thread() {
                @Override
                public void run() {
                    System.out.println("...............");
                    //线程2可以启动运行，但是进入不了printString方法了。因为该方法被锁定了
                    object.printString();
                }
            };
            thread2.start();        
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

yield方法：

线程优先级：

守护线程：