Java中的 MatchResult groupCount() 方法及示例

MatchResult 接口的groupCount()方法用于获取此匹配器模式中捕获组的数量。此方法返回一个整数值，它是匹配此匹配器时找到的组数。
句法：

public int groupCount()

参数：此方法不带任何参数。
返回值：此方法返回此匹配器模式中的捕获组数。
下面的示例说明了 MatchResult.groupCount() 方法：
示例 1：

Java

// Java code to illustrate groupCount() method
 
import java.util.regex.*;
 
public class GFG {
    public static void main(String[] args)
    {
 
        // Get the regex to be checked
        String regex = "(Geeks)";
 
        // Create a pattern from regex
        Pattern pattern
            = Pattern.compile(regex);
 
        // Get the String to be matched
        String stringToBeMatched
            = " GeeksForGeeks Geeks for For Geeks Geek";
 
        // Create a matcher for the input String
        MatchResult matcher
            = pattern
                  .matcher(stringToBeMatched);
 
        // Get the number of capturing groups
        // using groupCount() method
        System.out.println(matcher.groupCount());
    }
}

输出：

1

示例 2：

Java

// Java code to illustrate groupCount() method
 
import java.util.regex.*;
 
public class GFG {
    public static void main(String[] args)
    {
 
        // Get the regex to be checked
        String regex = "GFG";
 
        // Create a pattern from regex
        Pattern pattern
            = Pattern.compile(regex);
 
        // Get the String to be matched
        String stringToBeMatched
            = "FGF GF FG FGF";
 
        // Create a matcher for the input String
        MatchResult matcher
            = pattern
                  .matcher(stringToBeMatched);
 
        // Get the number of capturing groups
        // using groupCount() method
        System.out.println(matcher.groupCount());
    }
}

输出：

0

参考： https://docs.oracle.com/javase/9/docs/api/ Java/util/regex/Matcher.html#groupCount–