Question

我正在尝试实现自己的ArrayDeque，完全了解utils.ArrayDeque可用。（这是一个学校项目）。我创建了似乎是ArrayDeque的工作实现。我的问题是尝试创建一个ArrayDeque的子节点，当它完整而不是抛出异常时会增长。当它增长时，索引是正确的（？），但我的数组顺序没有意义。

下面是该项目的链接，相关代码位于。 https://github.com/tagptroll1/Oblig1/tree/master/src/Deque

//From ResizeableArrayDeque
private void growArray(){
    int newCapacity = deque.length * 2;
    if (newCapacity >= MAX_CAPACITY){
        throw new DequeFullException("Tried to expand deque past MAX Capacity");
    }
    //deque = Arrays.copyOf(deque, newCapacity);
    @SuppressWarnings("unchecked")
    E[] tempDeque = (E[]) new Object[newCapacity];
    for (int i = deque.length; i > 0; i--){
        if (!isArrayEmpty()){
            tempDeque[i] = pullLast();
        } else {
            throw new DequeEmptyException("Tried to pull element from empty deque");
        }
    }
    deque = tempDeque;
    topIndex = 0;
    botIndex = numberOfEntries;
}

@Override
public void addFirst(E elem){
    if (isArrayFull()){
        growArray();
    }
    deque[topIndex = dec(topIndex, deque.length)] = elem;
    numberOfEntries ++;
}

@Override
public void addLast(E elem){
    if (isArrayFull()){
        growArray();
    }
    deque[botIndex] = elem;
    numberOfEntries ++;
    botIndex = inc(botIndex, deque.length);
}

// From ArrayDeque
protected static int inc(int i, int modulus) {
    if (++i >= modulus) {
        i = 0;
    }
    return i;
}


protected static int dec(int i, int modulus) {
    if (--i < 0) {
        i = modulus - 1;
    }
    return i;
}

我没有看到如何将旧数组复制到新的更大的数组，因为排序不适用于之后添加的新元素。下面是阵列的测试打印：

 Adding [a, b, c, d] to deques bottom
Adding: 0 arrayIndex to 1. tail-index, element: a
[a] [null] [4] [3] [2] [1] 
Adding: 1 arrayIndex to 2. tail-index, element: b
[a] [b] [4] [3] [2] [1] 
Adding: 2 arrayIndex to 1. tail-index, element: c
[c] [4] [3] [2] [1] [a] [b] [null] [null] [null] [null] [null] 
Adding: 3 arrayIndex to 2. tail-index, element: d
[c] [d] [3] [2] [1] [a] [b] [null] [null] [null] [null] [null] 
Current Tail index is 2

Answer 1

问题在于我忘记在从第一个数组拉出之前保存numberOfEntries，因为当我之后设置索引时该变量将为0。通过创建临时int来保存它直到传输完成时解决了问题

扩展一个圆形ArrayDeque

1 个答案: