Java Matcher start(int)用法及代碼示例

Matcher類的start(int group)方法用於從指定組中獲取已經完成的匹配結果的起始索引。

用法:

public int start(int group)

參數：此方法采用一個參數組，該參數組是要求匹配模式的起始索引的組。

返回值：此方法返回與指定組匹配的第一個字符的索引。

異常：該方法拋出：

IllegalStateException如果尚未嘗試匹配，或者先前的匹配操作失敗。
IndexOutOfBoundsException如果模式中沒有具有給定索引的捕獲組。

下麵的示例說明Matcher.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*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 first index of match result 
            System.out.println(matcher.start(1)); 
        } 
    } 
}

輸出：

Current Matcher: java.util.regex.Matcher[pattern=(G*s) region=0,13 lastmatch=]
4
12

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 
            = "GFGFGFGFGFGFGFGFGFG"; 
  
        // 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 first index of match result 
            System.out.println(matcher.start(0)); 
        } 
    } 
}

輸出：

Current Matcher: java.util.regex.Matcher[pattern=(G*G) region=0,19 lastmatch=]
0
2
4
6
8
10
12
14
16
18

參考： Oracle Doc

相關用法

注：本文由純淨天空篩選整理自Kirti_Mangal大神的英文原創作品 Matcher start(int) method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。