Java Matcher start(String)用法及代碼示例

Matcher類的start(String string)方法用於從指定的字符串獲取已經完成的匹配結果的起始索引。

用法:

public int start(String string)

參數：此方法采用參數字符串，該字符串是需要匹配模式的開始索引的字符串。

返回值：此方法返回與指定字符串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如果模式中沒有給定名稱的捕獲組。

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 = "\\b(?<Geeks>[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 first index of match result 
            System.out.println(matcher.start("Geeks")); 
        } 
    } 
}

輸出：

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

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 = "\\b(?<GFG>[A-Za-z\\s]+)"; 
  
        // 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("GFG")); 
        } 
    } 
}

輸出：

Current Matcher: java.util.regex.Matcher[pattern=\b(?[A-Za-z\s]+) region=0,22 lastmatch=]
3

參考： Oracle Doc

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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(String) 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。