Question

我正在使用Netbeans，而且我编写的方法并没有完全符合它的要求：

private ArrayList<String[]>ProductsInStock;

public void DisplayStock() {
    ArrayList<String[]> Sort = new ArrayList<String[]>();
    System.out.println("");
    for (int i = 0; i < ProductsInStock.size(); i++) {
        if (ProductsInStock.get(i)[2].equals(Products.get(ProductCodeCB.getSelectedIndex())[1])) {
            boolean foundColor = false;
            int size = Sort.size();//Since the size will differ dynamically
            for (int k = 0; k < size; k++) {
                if (Sort.get(k)[3].equals(ProductsInStock.get(i)[3])) {
                    foundColor = true;
                    if (Sort.get(k)[4].equals(ProductsInStock.get(i)[4])) {
                        String S[] = Sort.get(k);
                        S[5] = (Integer.parseInt(Sort.get(k)[5]) + Integer.parseInt(ProductsInStock.get(i)[5])) + "";
                        Sort.set(k, S);
                        break;
                    }
                    if (k == Sort.size() - 1) {
                        Sort.add(ProductsInStock.get(i));
                    }
                } else if (foundColor == true) {
                    Sort.add(k, ProductsInStock.get(i));
                    break;
                }
            }
            System.out.print(ProductsInStock.get(0)[5]+" ");
            if (foundColor == false) {
                Sort.add(ProductsInStock.get(i));
            }
        }
    }
}
}

该方法不应该更改ProductsInStock.get（0）[5]的值，但每次调用该方法时它都会递增1，我已经放置了“System.out.println（）”来显示你是如何实际改变价值的。结果如下：1 1 1 1 1 1 1 1 2 当我添加“S [5] = ProductsInStock.get（i）[5];”这一行时，结果变为：1 1 1 1 1 1 1 1 1（应该如此）：

public void DisplayStock() {
    ArrayList<String[]> Sort = new ArrayList<String[]>();
    System.out.println("");
    for (int i = 0; i < ProductsInStock.size(); i++) {
        if (ProductsInStock.get(i)[2].equals(Products.get(ProductCodeCB.getSelectedIndex())[1])) {
            boolean foundColor = false;
            int size = Sort.size();//Since the size will differ dynamically
            for (int k = 0; k < size; k++) {
                if (Sort.get(k)[3].equals(ProductsInStock.get(i)[3])) {
                    foundColor = true;
                    if (Sort.get(k)[4].equals(ProductsInStock.get(i)[4])) {
                        String S[] = Sort.get(k);
                        S[5] = (Integer.parseInt(Sort.get(k)[5]) + Integer.parseInt(ProductsInStock.get(i)[5])) + "";
                        Sort.set(k, S);
                        S[5]=ProductsInStock.get(i)[5]; //<<<<HERE>>>>
                        break;
                    }
                    if (k == Sort.size() - 1) {
                        Sort.add(ProductsInStock.get(i));
                    }
                } else if (foundColor == true) {
                    Sort.add(k, ProductsInStock.get(i));
                    break;
                }
            }
            System.out.print(ProductsInStock.get(0)[5]+" ");
            if (foundColor == false) {
                Sort.add(ProductsInStock.get(i));
            }
        }
    }
}

如您所见，没有一个“ProductsInStock.set（）”或“ProductsInStock.get（）[] =”来更改arraylist中的任何值。

Answer 1

当你这样写：

 Sort.add(ProductsInStock.get(i));

您要将ProductsInStock.get(i)数组的引用添加到Sort列表中。 Sort.get(Sort.size()-1)中所做的任何更改都会影响原始数组。

因此代码如

String S[] = Sort.get(k);
S[5] = ...

修改ProductsInStock List。

的其中一个数组

为了避免这种情况，您应该在将数组添加到其他列表之前创建数组的副本：

Sort.add(Arrays.copyOf(ProductsInStock.get(i),ProductsInStock.get(i).length));

错误或逻辑错误

1 个答案: