Java Matcher replaceFirst(String)用法及代码示例

Matcher类的replaceFirst(String)方法的行为类似于append-and-replace方法。此方法读取输入字符串，并将其替换为匹配字符串中的第一个匹配模式。

用法:

public String replaceFirst(String stringToBeReplaced)

参数：此方法采用参数stringToBeReplaced，它是匹配器中要替换的String。

返回值：此方法返回一个String，其目标String通过替换String进行构造。

下面的示例说明Matcher.replaceFirst()方法：

示例1:

// Java code to illustrate replaceFirst() 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); 
  
        System.out.println("Before Replacement: "
                           + stringToBeMatched); 
  
        // Get the String to be replaced 
        String stringToBeReplaced = "GFG"; 
        StringBuilder builder = new StringBuilder(); 
  
        // Replace every matched pattern 
        // with the target String 
        // using replaceFirst() method 
        System.out.println("After Replacement: "
                           + matcher 
                                 .replaceFirst(stringToBeReplaced)); 
    } 
}

输出：

Before Replacement: GeeksForGeeks Geeks for For Geeks Geek
After Replacement: GFGForGeeks Geeks for For Geeks Geek

示例2:

// Java code to illustrate replaceFirst() method 
  
import java.util.regex.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // Get the regex to be checked 
        String regex = "(FGF)"; 
  
        // Create a pattern from regex 
        Pattern pattern 
            = Pattern.compile(regex); 
  
        // Get the String to be matched 
        String stringToBeMatched 
            = "FGF FGF FGF FGF"; 
  
        // Create a matcher for the input String 
        Matcher matcher 
            = pattern.matcher(stringToBeMatched); 
  
        System.out.println("Before Replacement: "
                           + stringToBeMatched); 
  
        // Get the String to be replaced 
        String stringToBeReplaced = "GFG"; 
        StringBuilder builder 
            = new StringBuilder(); 
  
        // Replace every matched pattern 
        // with the target String 
        // using replaceFirst() method 
        System.out.println("After Replacement: "
                           + matcher 
                                 .replaceFirst(stringToBeReplaced)); 
    } 
}

输出：

Before Replacement: FGF FGF FGF FGF
After Replacement: GFG FGF FGF FGF

参考： https://docs.oracle.com/javase/9/docs/api/java/util/regex/Matcher.html#replaceFirst-java.lang.String-

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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 replaceFirst(String) 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。