java - 用数组方法切换

Question

这是我第一次使用数组，我对如何在此设置中使用数组感到困惑。我尝试使用 switch，但我不确定它如何使用不同的情况等。当涉及到使用 [] 的数组时，也不确定 java 知道或不知道什么。谁能告诉我我的想法是否正确，或者我是否完全不对。

public class Sum3 {
    // TODO - write your code below this comment.
    // You will need to write a method that will take
    // an array of int, and will return the sum of
    // the first three elements.  NOTE THAT
    // THE ARRAY LENGTH MAY BE SMALLER THAN 3.
    // In the event that the array isn't long enough,
    // substitute 0s for the missing elements.
    // For example:
    // - if the array is empty you should return 0 (0 + 0 + 0 = 0),
    // - if the array contains only one element, you should
    //   return that element (element + 0 + 0 = element)
    // - if the array contains only two elements, you
    //   should return the sum of those two elements
    //   (first + second + 0 = first + second)
    // - if the array contains three or more elements,
    //   you should return the sum of the first three.
    //
    // You may be given an array which holds more than
    // three elements.  These extra elements (beyond three)
    // should be ignored.
    //
    // As a hint, switch may be useful here (though you
    // are not required to use it).
    //
    public static int array(int[] array) {
    switch (array) {
    case 0:
        return 0;
    case 1:
        return ([0]);
    case 2:
        return ([0]+[1]);
    case 3:
        return ([0]+[1]+[2]);

    // DO NOT MODIFY main!
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int[] array = new int[3];
        System.out.print("Enter first integer: ");
        array[0] = input.nextInt();
        System.out.print("Enter second integer: ");
        array[1] = input.nextInt();
        System.out.print("Enter third integer: ");
        array[2] = input.nextInt();
        System.out.println("Sum: " + sumUpToFirst3(array));
    }
}

Answer 1

它甚至看起来不像您粘贴的代码可以编译，但这里是 sumUpToFirst3 的一个简单实现，我认为它应该可以工作:

public int sumUpToFirst3(int[] array) {
    if (array == null) {
        return 0;
    }

    int upperBound = array.length > 3 ? 3 : array.length;
    int sum = 0;

    for (int i=0; i < upperBound; ++i) {
        sum += array[i];
    }

    return sum;
}