Java中的 MatchResult start() 方法和示例

MatchResult 接口的start()方法用于获取已经完成的匹配结果的开始索引。

句法：

public int start()

参数：此方法不带任何参数。

返回值：该方法返回匹配的第一个字符的索引。0

异常：如果尚未尝试匹配，或者之前的匹配操作失败，则此方法抛出IllegalStateException 。

下面的示例说明了 MatchResult.start() 方法：

示例 1：

// Java code to illustrate start() method
  
import java.util.regex.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Get the regex to be checked
        String regex = "(G*k)";
  
        // Create a pattern from regex
        Pattern pattern
            = Pattern.compile(regex);
  
        // Get the String to be matched
        String stringToBeMatched = "Geeks";
  
        // Create a matcher for the input String
        MatchResult matcher
            = pattern
                  .matcher(stringToBeMatched);
  
        while (((Matcher)matcher).find()) {
            // Get the first index of match result
            System.out.println(matcher.start());
        }
    }
}

输出：

3

示例 2：

// Java code to illustrate start() method
  
import java.util.regex.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Get the regex to be checked
        String regex = "(G*G)";
  
        // Create a pattern from regex
        Pattern pattern
            = Pattern.compile(regex);
  
        // Get the String to be matched
        String stringToBeMatched = "GFG";
  
        // Create a matcher for the input String
        MatchResult matcher
            = pattern
                  .matcher(stringToBeMatched);
  
        while (((Matcher)matcher).find()) {
            // Get the first index of match result
            System.out.println(matcher.start());
        }
    }
}

输出：

0
2

=