你如何修复陷入困境的Thread Join()

Question

我是多线程的新手,我只是尝试使用线程打印14000大小的字符串Arraylist来实践练习.我不是在考虑这个问题的效率,也不考虑有用性; 我只是想了解线程概念.

我的输出非常错误,我尝试了各种同步和其他失败的尝试.我现在遇到了一个名为join的工具,但是我的程序没有退出并继续运行.我调试了代码,程序只是卡在第一个线程连接上,我想不出任何理由或解决方案来解决问题.

我解决问题的方法是创建4个线程来分割打印任务.然后我会等到所有线程都完成并在关闭输出文件之前使用连接权限.

public class Threadprinting implements Runnable{
private static List<String> list;
private Thread T1,T2,T3,T4;
public void printinput(List<String> store){
    list=new ArrayList<String>(store);
    Threadprinting threadprinting=new Threadprinting();
    Threadprinting.generatethreads();   
}

public void generatethreads() {
    T1=new Thread(this,"t1");
    T1.start();
    T2=new Thread(this,"t2");
    T2.start();
    T3=new Thread(this,"t3");
    T3.start();
    T4=new Thread(this,"t4");
    T4.start();
}

public void run(){
    try {               
        PrintWriter out = new PrintWriter(new FileWriter("Output.txt"));
        switch (Thread.currentThread().getName()) {
            case "t1":
                System.out.println("Thread "+ Thread.currentThread().getName() + " is running");
                for (int i = 0; i < list.size() / 4; i++) {
                    out.println((list.get(i)));
                }
                break;
            case "t2":
                System.out.println("Thread "+ Thread.currentThread().getName() + " is running");
                for (int i = list.size() / 4; i < list.size() / 2; i++) {
                    out.println((list.get(i)));
                }
                break;
            case "t3": 
                System.out.println("Thread "+Thread.currentThread().getName()+" is running");
                for (int i = list.size()/2; i < list.size()/4+list.size()/2; i++) {
                    out.println((list.get(i)));
                }
                break;
            case "t4": 
                System.out.println("Thread "+Thread.currentThread().getName()+" is running");
                for (int i = list.size()/4+list.size()/2; i < list.size(); i++) {
                    out.println((list.get(i)));
                }
                break;
            default:
                System.out.println("filler");
                break;
            }
            jointhreads();
            out.close();
    }
    catch(IOException e){
        System.out.println("problem came from here");
    }
}

特别:

private void jointhreads() {
    try {
        T1.join();
        T2.join();
        T3.join();
        T4.join();
    } catch (InterruptedException e) {
        System.out.println("the joins failed");
    }
}

}

根据调试器,程序无法终止并继续在T1.join上运行.

Answer 1

您正在调用jointhreads要加入的内部线程,因此 T1基本上等待T1(本身)终止但这种情况永远不会发生.

您应该jointrheads在主线程中调用,因此应用程序将等待所有工作线程完成其工作