如何获取不为null的数组元素 [英] How to get elements of an array that is not null

问题描述

我正在使用数组进行礼物(字符串型)存储，最大存储量为5亿个.我想获取数组中已使用元素的数量，例如当前有多少礼物，(即我存储了253538个礼物，但我不知道.Java中是否有一个命令可以知道只有253538个包含元素的数组中的插槽).但是我不知道该怎么办.这是我要使用的代码片段:

I am doing gift (String-type) storage, using arrays, with the maximum 500 million. I want to get the number of used elements in an array like how many gifts are currently in stock, (I.E. I stored 253538 gifts, but I don't know that. Is there a command in Java that can know that there is only 253538 Slots in the array that contain an element). But I don't know how to. Here's the snippet of code I want to use:

static String[] Gifts = new String[500000000];
static int i = 0;
String command, Gift;
while (true) {
    //Gift Array Console
    String command = scan.next();
    if (command == "addgift") {
        String Gift = scan.next();
        Gifts[i] = Gift;
        i++;
    }
}

推荐答案

您可以遍历数组并计算已初始化的数组元素.

You can iterate through the array and count the initialized array elements.

int counter = 0;
for (int i = 0; i < arrayName.length; i ++)
    if (arrayName[i] != null)
        counter ++;

如果您使用 ArrayList< String> ，那就更好了，因此您可以使用 size()

Also it would be even better if you used ArrayList<String> so you could use size()

ArrayList<String> arrayName = new ArrayList<String>(20);
System.out.println(arrayName.size());

由于未将任何元素添加到ArrayList，因此它将打印0.

It will print 0, as there are no elements added to the ArrayList.

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