栈的压入、弹出序列

public boolean IsPopOrder(int[] pushSequence, int[] popSequence) {
    int n = pushSequence.length;
    Stack<Integer> stack = new Stack<>();
    for (int pushIndex = 0, popIndex = 0; pushIndex < n; pushIndex++) {
        stack.push(pushSequence[pushIndex]);
        while (popIndex < n && !stack.isEmpty() 
                && stack.peek() == popSequence[popIndex]) {
            stack.pop();
            popIndex++;
        }
    }
    return stack.isEmpty();
}