Java 访问封闭作用域中的局部变量 [重复]

Question

我在Java中的TimerTask遇到了一些问题。基本上，我试图做的是为每个会话计算一些东西，我设置一分钟的时间范围，一旦时间到了，我会提示用户输入是否启动另一个会话。以下是我尝试过的：

    String toCont = "";
    Scanner scanner = new Scanner(System.in);
    
    do {
        long delay = TimeUnit.MINUTES.toMillis(1);
        Timer t = new Timer();
        int marks = startSession(); // function to compute some marks
        
        TimerTask task = new TimerTask() {
            @Override
            public void run() {
                System.out.println("Time's up!");
                System.out.print("Do you wished to start a new game? (Y/N): ");
                toCont = scanner.next();
            }
        };
        t.schedule(task, delay);

    } while (toCont.equals("y") || toCont.equals("Y"));

但是，run（）中的toCont变量出现了一些语法错误。错误消息如下：“封闭范围中定义的局部变量toCont必须是final或有效final”。有什么办法可以解决这个问题吗？谢谢

Answer 1

要在内部类中使用变量，必须将其声明为final。将它添加到do while循环中(解决方法)

do {
        long delay = TimeUnit.MINUTES.toMillis(1);
        final Integer innertoCont = new Integer(toCont);
        Timer t = new Timer();
        int marks = startSession(); // function to compute some marks
        
        TimerTask task = new TimerTask() {
            @Override
            public void run() {
                System.out.println("Time's up!");
                System.out.print("Do you wished to start a new game? (Y/N): ");
                innertoCont = scanner.next();
            }
        };
        t.schedule(task, delay);

    } while (toCont.equals("y") || toCont.equals("Y"));

Answer 2

使变量成为最终的单元素数组。

final String[] toCont = {
    ""
};
Scanner scanner = new Scanner(System.in);

do {
    long delay = TimeUnit.MINUTES.toMillis(1);
    Timer t = new Timer();
    int marks = startSession(); // function to compute some marks

    TimerTask task = new TimerTask() {
        @Override
        public void run() {
            System.out.println("Time's up!");
            System.out.print("Do you wished to start a new game? (Y/N): ");
            toCont[0] = scanner.next();
        }
    };
    t.schedule(task, delay);

} while (toCont[0].equals("y") || toCont[0].equals("Y"));