Question

我正在尝试打印多少字母“a”。它一直给我0 ...任何帮助？

JFileChooser chooser = new JFileChooser();
if (chooser.showOpenDialog(null) == JFileChooser.APPROVE_OPTION) {
    File myfile = chooser.getSelectedFile();
    try {

        Scanner in = new Scanner(myfile);
        String word = in.nextLine();
        int counter = 0;
        for (int i = 0; i < word.length(); i++) {
            if (word.charAt(i) == 'a') {
                counter++;
            }
        }

        System.out.println("# of chars: " + counter);
    } catch (IOException e) {
        System.err.println("A reading error occured");
    }
}

Answer 1

计算char出现次数的更简单（一行）方式是：

int count = word.replaceAll("[^a]", "").length();

这会将每个不是“a”的字符替换为空白 - 有效地删除它 - 留下一个只包含原始字符串的“a”字符的字符串，然后你得到它的长度。

Answer 2

除了阅读文件的任何问题外，还可以尝试使用StringUtils countMatches。它已经在常见的语言中了，请注意使用它。

例如

int count = StringUtils.countMatches(word, "a");

Answer 3

JFileChooser chooser = new JFileChooser();
if (chooser.showOpenDialog(null) == JFileChooser.APPROVE_OPTION) {
File myfile = chooser.getSelectedFile();
try {

    Scanner in = new Scanner(myfile);

    int counter = 0;
while(in.hasNextLine()){
 String word = in.nextLine();
    for (int i = 0; i < word.length(); i++) {
        if (word.charAt(i) == 'a') {
            counter++;
        }
    }
}

    System.out.println("# of chars: " + counter);
} catch (IOException e) {
    System.err.println("A reading error occured");
}
}

计算字符串中的字符出现次数

3 个答案: