Java 学习笔记之 Stop停止线程

Stop停止线程:

使用stop()方法停止线程是非常暴力的，会抛出java.lang.ThreadDeath Error，但是我们无需显示捕捉, 以下捕捉只是为了看得更清晰。

public class StopThread 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) {
            System.out.println("Stop thread. Interrupted status: " + this.isInterrupted());
            e.printStackTrace();
        } catch (Error e){
            System.out.println("Enter error. Interrupted status: " + this.isInterrupted());
            e.printStackTrace();
        }
    }
}

public class ThreadRunMain {
    public static void main(String[] args) {
        testStopThread();
    }

    public static void testStopThread(){
        try {
            StopThread st = new StopThread();
            st.start();
            Thread.sleep(5000);
            st.stop();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

运行结果：

stop()方法已经被作废，因为如果暴力让线程停止可能会使一些清理性的工作得不到完成。其次，可能会造成数据不一致的问题。如下例：

public class SynchronizedObject {
    private String username = "a";
    private String password = "aa";

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    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 StopThreadIssue extends Thread{
    private SynchronizedObject object;

    public StopThreadIssue(SynchronizedObject object) {
        super();
        this.object = object;
    }

    @Override
    public void run() {
        object.printString("b", "aa");
    }
}

public class ThreadRunMain {
    public static void main(String[] args) {
        testStopThreadIssue();
    }

    public static void testStopThreadIssue(){
        try {
            SynchronizedObject object = new SynchronizedObject();
            StopThreadIssue sti = new StopThreadIssue(object);
            sti.start();
            Thread.sleep(500);
            sti.stop();
            System.out.println(object.getUsername() + " " + object.getPassword());
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }
}

运行结果：

我们期望的结果应该是：b bb，可是由于强制停止，导致 this.password = password; 没有执行。显然stop()在功能上具有缺陷，所以不建议在程序中使用stop()方法。