java - 私有(private)函数应该如何做参数验证或者用户输入和内部数据结构？

Question

以下代码将返回总和为 x 的整数对，例如:如果 arr {1, 2, 3, 4, 5] 且 x 为 7，则列表应包含 {3, 4} 和 {2, 5 }。主要目标是了解如何在私有(private)方法中执行参数验证。问题嵌套在评论中，请将建议限制为仅提出的问题。感谢您深入研究代码来检查我的问题。

public static List<Pair> getPairsFromPositiveArray(int[] arr, int x) {
    // check for all positive integers
    for (int i : arr) {   // if arr is null, then this loop would throw NPE. So no need to make an exclicit check for null.
        if (i < 0) throw new IllegalArgumentException("No integer should be negative.");
    }
    final List<Pair> list = new ArrayList<Pair>();
    getPair(arr, x, list);
    return list;
}

private static void getPair(int[] arr, int x, List<Pair> list) {
    // QUESTION 1: Should check of "all positive integers" be done here too ?

    /*
     * QUESTION 2: 
     * list is data structure which we created internally ( user did not provide it )  
     * Does anyone suggest, it throw an NPE or do an explicit assert check for list != null ? 
     */
    assert list != null;  // form my understanding of e effective java. 
    assert arr != null;   // form my understanding of e effective java. 

    final Set<Integer> set = new HashSet<Integer>();
    /*
     * QUESTION 3:
     * arr is a data structure which was input by the user.
     * Should we check for assert arr != null or let loop throw a NPE ?
     */
    for (int i : arr) { 
        if (set.contains(i)) {
            System.out.println(i + " : ");
            list.add(new Pair(i, x - i));
        } else {
            set.add(x - i);
        }
    }
}

Answer 1

QUESTION 1: Should check of "all positive integers" be done here too ?

答:不；因为您将在 getPair() 之前调用 getPairsFromPositiveArray() 来获取列表

QUESTION 2: * list is data structure which we created internally ( user did not provide it )
* Does anyone suggest, it throw an NPE or do an explicit assert check for list != null ?

答:断言

QUESTION 3: * arr is a data structure which was input by the user. * Should we check for assert arr != null or let loop throw a NPE

答:

• 始终执行健全性检查...所以是的，请检查 arr != null

• 总是更喜欢断言而不是抛出 NPE