Question

我有一条前线 HelloxyzxyzxyzHello

我有一个以下正则表达式匹配此行

Map<Character, Integer> map = new HashMap();
for (char c: cs) {
    Integer iCnt = map.get(c);
    if (iCnt ==  null) {
        map.put(c, 1);                
    } else {
        map.put(c, ++iCnt);
    }
}

现在我想得到xyz的数量在我的行中它是3

除了查找每个匹配的模式并使用计数器之外，是否有可从regex获得的现成API。

Answer 1

试试这个：

import java.util.regex.*;

class Test {
    public static void main(String[] args) {
        String hello = "HelloxyzxyzxyzHello";
        Pattern pattern = Pattern.compile("xyz");
        Matcher  matcher = pattern.matcher(hello);

        int count = 0;
        while (matcher.find())
            count++;

        System.out.println(count);    // prints 3
    }
}

编辑：捕获群组

String line = "This order was placed for QT3000! OK?";
Pattern pattern = Pattern.compile("(.*?)(\\d+)(.*)");
Matcher matcher = pattern.matcher(line);
while (matcher.find()) {
    System.out.println("group 1: " + matcher.group(1));
    System.out.println("group 2: " + matcher.group(2));
    System.out.println("group 3: " + matcher.group(3));
}

Answer 2

您可以尝试使用以下正则表达式来获取两个xyz子字符串中存在的所有Hello计数。

import java.util.regex.*;

class Test {
    public static void main(String[] args) {
        String hello = "HelloxyzxyzxyzHello";
        Pattern pattern = Pattern.compile("(?:Hello|(?<!^)\\G)(?:(?!Hello).)*?(xyz)(?=.*?Hello)");
        Matcher  matcher = pattern.matcher(hello);

        int count = 0;
        while (matcher.find()) {
            if (matcher.group(1)) {
            count++;
             }
         }
        System.out.println(count);    // prints 3
    }
}

DEMO

使用regex java计算给定行中的特定字符串

2 个答案: