计算ArrayList中一系列字符串中出现的某个字母的数量 [英] Counting the number of a certain letter appears in series of strings in an ArrayList

问题描述

我有一个 ArrayList 以做盘子"的形式存储笔记(字符串).我有一个带有方法的笔记类，该方法应该遍历 ArrayList 中的所有笔记并计算某个字母出现的次数.这是我目前写的方法:

I have an ArrayList that stores notes (strings) in the form of "do the dishes". I have a notes class with a method that is supposed to go through all the notes in the ArrayList and count the number of times a certain letter appears. This is the method I have written so far:

public int countNumberOf(String letter) {
        int count = 0;
        for (int i = 0; i < notes.size(); i++) {
            String note = (notes.get(i));
            for (int j = 0; i < note.length(); i++) {
                String letterTemp = note.substring(i, i);
                if (letterTemp.equalsIgnoreCase(letter)) {
                    count++;
                }
            }

        }
        return count;
    }

但是，当我运行该程序时，即使我知道它出现在 ArrayList 中，字母a"出现的次数也为零.我做错了什么?

However, when I run the program, I'm getting zero for the number of times the letter "a" appears even though I know it's present in the ArrayList. What am I doing wrong?

推荐答案

与将 String 传递给方法并执行 substring 不同，您始终可以访问和比较字符，例如:

Instead of passing a String to a method and doing a substring, you can always access and compare the characters, e.g.:

public int countNumberOf(char letter) {
...
String letterTemp = note.charAt(i);
if (letter == letterTemp) {
        count++;
}

另一个例子:

public static int countOccurrences(String text, char character) {
    int count = 0;
    for (int i = 0; i < text.length(); i++) {
        if (text.charAt(i) == character) {
            count++;
        }
    }
    return count;
}

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