计算给定字符串在 ArrayList 中的出现次数 [英] Count occurrences of a given string in an ArrayList

问题描述

我有一个字符串列表，我浏览它并计算x"字符串的数量，如下所示，但计数没有打印出预期值:

I have a list of strings , I browse it and count number of "x" strings as below but the count doesn't print me the expected value:

ArrayList<Integer> list = new ArrayList<Integer>();

List<String> strings = table.getValue(); //this gives  ["y","z","d","x","x","d"]

int count = 0;
for (int i = 0; i < strings.size(); i++) {
    if ((strings.get(i) == "x")) {
        count++;
        list.add(count);
    }
}

System.out.println(list);

这给 [] 它应该是 2，因为我有 2 次出现x"

this gives [] it should be 2 as I have 2 occurrences of "x"

推荐答案

已经有一个 现有方法:

Collections.frequency(collection, object);

在你的情况下，像这样使用(用这个替换你发布的所有代码):

In your case, use like this (replace all of your posted code with this):

System.out.println(java.util.Collections.frequency(table.getValue(), "x"));

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