Java中获取一个字符串在另一个字符串出现的次数

在Java中，要获取一个字符串在另一个字符串中出现的次数，可以使用多种方法。以下是几种常见的方法：

1. 使用`indexOf()`方法：

public class StringOccurrences {
    public static int countOccurrences(String mainString, String subString) {
        int count = 0;
        int index = 0;

        while ((index = mainString.indexOf(subString, index)) != -1) {
            count++;
            index += subString.length();
        }

        return count;
    }

    public static void main(String[] args) {
        String mainString = "Hello, this is a test. This test is simple.";
        String subString = "test";
        int occurrences = countOccurrences(mainString, subString);
        System.out.println("Occurrences of \"" + subString + "\": " + occurrences);
    }
}

2. 使用`split()`方法：

public class StringOccurrences {
    public static int countOccurrences(String mainString, String subString) {
        if (subString.isEmpty()) {
            return 0;
        }
        String[] parts = mainString.split(Pattern.quote(subString));
        return parts.length - 1;
    }

    public static void main(String[] args) {
        String mainString = "Hello, this is a test. This test is simple.";
        String subString = "test";
        int occurrences = countOccurrences(mainString, subString);
        System.out.println("Occurrences of \"" + subString + "\": " + occurrences);
    }
}

3. 使用正则表达式：

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class StringOccurrences {
    public static int countOccurrences(String mainString, String subString) {
        Pattern pattern = Pattern.compile(Pattern.quote(subString));
        Matcher matcher = pattern.matcher(mainString);
        int count = 0;
        while (matcher.find()) {
            count++;
        }
        return count;
    }

    public static void main(String[] args) {
        String mainString = "Hello, this is a test. This test is simple.";
        String subString = "test";
        int occurrences = countOccurrences(mainString, subString);
        System.out.println("Occurrences of \"" + subString + "\": " + occurrences);
    }
}

这些方法都可以用来计算一个字符串在另一个字符串中出现的次数。你可以根据具体需求选择合适的方法。