.replaceFirst()

The .replaceFirst() method replaces the first matching substring in a string with the specified replacement string.

Syntax

string.replaceFirst(String substring, String replacement);

The .replaceFirst() method takes two parameters:

• substring, a string or a regular expression to specify which substring needs to be replaced.

Note: In regular expressions, some characters, for example, the asterisk (*) or the question mark (?), have special meanings. To match a substring with these special characters, they must be “escaped” with the backslash (\) character, or the ‘Matcher.quoteReplacement(String)` method can be used to get the string literal of any string passed as a parameter.

• replacement, a string to specify the substring to be substituted.

The .replaceFirst() method returns a string with the replaced substring, and it only replaces the first matching occurrence of the substring, while .replaceAll() replaces all matching occurrences of the substring.

Example

The example below replaces the first occurrence of the substring pizza in myString with the string donut and prints the results.

public class Main {
  public static void main(String[] args) {
    String myString = "I love pizza. I eat pizza every day. I make my own pizza.";
    String substring = "pizza";
    String replacement = "donut";

    String replacedString = myString.replaceFirst(substring, replacement);

    System.out.println("Original string: " + myString );
    System.out.println("Replaced string: " + replacedString);
  }
}

This results in the following output:

Original string: I love pizza. I eat pizza every day. I make my own pizza.
Replaced string: I love donut. I eat pizza every day. I make my own pizza.