Matcher replaceAll(String) method in Java with Examples

The replaceAll(String) method of Matcher Class behaves as a append-and-replace method. This method reads the input string and replace it with the matched pattern in the matcher string.

Syntax:

public String replaceAll(String stringToBeReplaced)

Parameters: This method takes a parameter stringToBeReplaced which is the String to be replaced in the matcher.

Return Value: This method returns a String with the target String constructed by replacing the String.

Below examples illustrate the Matcher.replaceAll() method:

Example 1:

// Java code to illustrate replaceAll() 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 replaceAll() method
        System.out.println("After Replacement: "
                           + matcher
                                 .replaceAll(stringToBeReplaced));
    }
}

Output:

Before Replacement: GeeksForGeeks Geeks for For Geeks Geek
After Replacement: GFGForGFG GFG for For GFG Geek

Example 2:

// Java code to illustrate replaceAll() 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
            = "GFGFGFGFGFGFGFGFGFG FGF GFG GFG FGF";

        // Create a matcher for the input String
        Matcher matcher
            = pattern.matcher(stringToBeMatched);

        // Get the String to be replaced
        String stringToBeReplaced = "GFG";
        StringBuilder builder
            = new StringBuilder();

        // Replace every matched pattern
        // with the target String
        // using replaceAll() method
        System.out.println("After Replacement: "
                           + matcher
                                 .replaceAll(stringToBeReplaced));
    }
}

Output:

After Replacement: GGFGGGFGGGFGGGFGGFG GFG GFG GFG GFG

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