java - 线程化 ArrayIndexOutofBoundException

Question

我创建了一个像这样的堆栈类。有时它会运行，有时会通过 ArrayIndexOutofBoundException 运行。线程中有什么问题？不太明白，请帮忙。

public class StackImpl<E> implements Stack<E>{

private E[] stackArray;

private int topOfStack;

public StackImpl(int size) {
    stackArray = (E[]) new Object[size];
    topOfStack = -1;
}

public synchronized void push(E e) {
    while (isFull()) {
        try {
            System.out.println("stack is full cannot add " + e);
            wait();
        } catch (InterruptedException exception) {
            exception.printStackTrace();
        }
    }
    stackArray[++topOfStack] = e;
    System.out
            .println(Thread.currentThread() + " :notifying after pushing");
    notify();
}

public boolean isEmpty() {
    return topOfStack == 0;
}

public synchronized E pop() {
    while (isEmpty()) {
        try {
            System.out.println("stack is empty cannot pop ");
            wait();
        } catch (InterruptedException e) {

        }
    }
    System.out.println(topOfStack);
    E element = stackArray[topOfStack];
    stackArray[topOfStack--] = null;
    System.out.println(Thread.currentThread() + " notifying after popping");
    notify();
    return element;
}

public boolean isFull() {
    return topOfStack >= stackArray.length-1;
}

public static void main(String[] args) {
    final Stack<Integer> stack = new StackImpl<Integer>(10);
    (new Thread("Pusher") {
        public void run() {
            while (true) {
                stack.push(10);
            }
        }
    }).start();
    (new Thread("Popper") {
        public void run() {
            while (true) {
                stack.pop();
            }
        }
    }).start();
}

}

Answer 1

你设置

topOfStack = -1;

在 StackImpl 的构造函数中，但你的 isEmpty 方法检查是否为 0:

public boolean isEmpty() {
    return topOfStack == 0;
}

因此，如果推送器尚未添加任何值，则 while 循环将在第一次弹出时失败:

    public synchronized E pop() {
        while (isEmpty()) {
            try {
                System.out.println("stack is empty cannot pop ");
                wait();
            } catch (InterruptedException e) {

            }
        }

设置 topOfStack在构造函数中设置为 0，它应该可以工作。

编辑:想起来，改为更改 isEmpty -方法return topOfStack < 0; ，然后留下topOfStack = -1;在你的构造函数中...否则索引 0 中的元素永远不会弹出。