Java中的 Matcher group(String) 方法及示例

Matcher 类的group(String 字符串)方法用于从指定的字符串中获取已经完成的匹配结果组。

句法：

public String group(String string)

参数：此方法采用参数字符串，该字符串是需要匹配模式的组索引的字符串。

返回值：该方法从指定的字符串返回匹配组的组。

异常：此方法抛出：

• 如果尚未尝试匹配，或者之前的匹配操作失败，则IllegalStateException 。
• 如果模式中没有具有给定名称的捕获组，则出现IndexOutOfBoundsException 。

下面的示例说明了 Matcher.group() 方法：

示例 1：

// Java code to illustrate end() method
  
import java.util.regex.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Get the regex to be checked
        String regex = "\\b(?[A-Za-z\\s]+)";
  
        // Create a pattern from regex
        Pattern pattern
            = Pattern.compile(regex);
  
        // Get the String to be matched
        String stringToBeMatched
            = "GeeksForGeeks";
  
        // Create a matcher for the input String
        Matcher matcher
            = pattern
                  .matcher(stringToBeMatched);
  
        // Get the current matcher state
        MatchResult result
            = matcher.toMatchResult();
        System.out.println("Current Matcher: "
                           + result);
  
        while (matcher.find()) {
            // Get the group matched using group() method
            System.out.println(matcher.group("Geeks"));
        }
    }
}

输出：

Current Matcher: java.util.regex.Matcher[pattern=\b(?[A-Za-z\s]+) region=0,13 lastmatch=]
GeeksForGeeks

示例 2：

// Java code to illustrate end() method
  
import java.util.regex.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
       // Get the regex to be checked
        String regex = "\\b(?[A-Za-z\\s]+)";
  
        // Create a pattern from regex
        Pattern pattern
            = Pattern.compile(regex);
  
        // Get the String to be matched
        String stringToBeMatched
            = "GFG FGF GFG";
  
        // Create a matcher for the input String
        Matcher matcher
            = pattern
                  .matcher(stringToBeMatched);
  
        // Get the current matcher state
        MatchResult result
            = matcher.toMatchResult();
        System.out.println("Current Matcher: "
                           + result);
  
        while (matcher.find()) {
            // Get the group matched using group() method
            System.out.println(matcher.group("GFG"));
        }
    }
}

输出：

Current Matcher: java.util.regex.Matcher[pattern=\b(?[A-Za-z\s]+) region=0,11 lastmatch=]
GFG FGF GFG

参考： Oracle 文档