java - 线程返回值永久检查

Question

我实现了一个 Runnable，如果 boolean 值变为 true，它会检查正确性。

但我想将此值返回到我启动线程的类。

我注意到我可以使用 Future Callables 返回一个值，使用它们我可以计算一些东西并立即返回它，但我无法永久检查该值是否变为 true。

我怎样才能实现这个目标？

感谢您的帮助。

public class ResultChecker implements Runnable{
    private DrawView drawView;

    public ResultChecker(DrawView drawView){
        this.drawView = drawView;
    }

    public void run() {
        boolean run = true;
        while(run){
            if(drawView.isNextQuestion()){
                //RETURN VALUE HERE
                run = false;
            }
        }
    }

}

Answer 1

如果您想要轮询，请在 ResultChecker 中创建一个方法，该方法可以由需要返回值的线程调用。

public class ResultChecker implements Runnable{
    private DrawView drawView;
    private volatile Result r;

    public ResultChecker(DrawView drawView){
        this.drawView = drawView;
        this.r = null;
    }

    public Result poll() {
        return r;
    }

    public void run() {
        boolean run = true;
        while(run){
            if(drawView.isNextQuestion()){
                //RETURN VALUE HERE
                r = someObject;
                // once r has been assigned, you cannot touch it again
                // or the object it refers to from this thread because
                // there are no locks
                run = false;
            }
        }
    }

}

轮询器将像这样轮询:

r = resultChecker.poll();
if(r != null) {
    // we have result
} else {
    // result is not ready
    // try again later
}

如果您想返回多个值，则必须使用队列对其进行扩展。