Matcher replace Java 中 First(函数)方法示例

原文:https://www . geeksforgeeks . org/matcher-replacefirst function-method-in-Java-with-examples/

匹配器类的替换第一个(函数)方法表现为一个追加和替换方法。此方法用参数中传递的函数替换匹配器中匹配的模式的第一个实例。

语法:

public String replaceFirst(
        Function replacerFunction)

参数:该方法取一个参数replace function，该函数定义了匹配器的替换。

返回值:该方法返回一个字符串，目标字符串通过替换字符串来构造。

异常:此方法抛出以下异常:

  • null 指针异常:你好你好空值
  • Concurrentmodification Exception : If it is detected that the replacer function has modified the state of this matcher.

下面的例子说明了 Matcher.replaceFirst()方法:

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 = "Geeks";
        StringBuilder builder
            = new StringBuilder();

        // Replace every matched pattern
        // with the target String
        // using replaceFirst() method
        System.out.println("After Replacement: "
                           + matcher
                                 .replaceFirst(
                                     x -> x.group().toUpperCase()));
    }
}

输出:

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

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
            = "GFG FGF GFG GFG 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(
                                     x -> x.group().toLowerCase()));
    }
}

输出:

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

参考:https://docs . Oracle . com/javase/9/docs/API/Java/util/regex/matcher . html # replace first-Java . util . function . function-

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