Java Matcher regionStart()用法及代码示例

Matcher类的regionStart()方法用于获取要与当前匹配器中的模式匹配的区域的startIndex。此方法返回一个整数值，该值是此匹配器区域的startIndex。

用法:

public int regionStart()

参数：此方法不带参数。

返回值：此方法返回一个整数值，该值是此匹配器区域的startIndex。

下面的示例说明Matcher.regionStart()方法：

示例1:

// Java code to illustrate regionStart() 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 
        Matcher matcher 
            = pattern.matcher(stringToBeMatched); 
  
        // Get previous startIndex of region 
        // using regionStart() method 
        System.out.println("Before changing region, "
                           + " Region starts from: "
                           + matcher.regionStart()); 
  
        // Restrict the region to 2, 10 
        matcher = matcher.region(2, 10); 
  
        // Get previous startIndex of region 
        // using regionStart() method 
        System.out.println("After changing region, "
                           + " Region starts from: "
                           + matcher.regionStart()); 
    } 
}

输出：

Before changing region,  Region starts from: 0
After changing region,  Region starts from: 2

示例2:

// Java code to illustrate regionStart() method 
  
import java.util.regex.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // Get the regex to be checked 
        String regex = "(F*F)"; 
  
        // Create a pattern from regex 
        Pattern pattern 
            = Pattern.compile(regex); 
  
        // Get the String to be matched 
        String stringToBeMatched 
            = "GFGFGFGFGFGFGFGFGFG FGF GFG GFG FGF"; 
  
        // Create a matcher for the input String 
        Matcher matcher 
            = pattern.matcher(stringToBeMatched); 
  
        // Get previous startIndex of region 
        // using regionStart() method 
        System.out.println("Before changing region, "
                           + " Region starts from: "
                           + matcher.regionStart()); 
  
        // Restrict the region to 5, 10 
        matcher = matcher.region(5, 10); 
  
        // Get previous startIndex of region 
        // using regionStart() method 
        System.out.println("After changing region, "
                           + " Region starts from: "
                           + matcher.regionStart()); 
    } 
}

输出：

Before changing region,  Region starts from: 0
After changing region,  Region starts from: 5

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

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注：本文由纯净天空筛选整理自Kirti_Mangal大神的英文原创作品 Matcher regionStart() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。