Java .replace()

The String class’ .replace() method returns a new string where all instances of a given value are switched with a new value.

Syntax

string.replace(char oldValue, char newValue);

A char represents a single character. Other valid inputs for the .replace() method include the following:

• An instance of the Character class that resolves to a single character.
• A CharSequence interface that represents a sequence of characters (the String class is one implementation of this interface).

In any case, the returned result will always be a new String object with all instances of oldValue replaced with the newValue.

Example

The example below tests a string s with the usage of char values, Character instances, and a CharSequence where a substring, “Hello”, is replaced with “Goodbye” and reassigned:

public class ReplaceMe {
  public static void main(String args[]) {
    String s = "Hello World!";
    System.out.println("Original String: " + s);

    char testA = 'e';
    System.out.println("With primitive char: " + s.replace(s.charAt(2), testA));

    Character testB = new Character('o');
    System.out.println("With Character class: " + s.replace(s.charAt(6), testB));

    CharSequence testC = "Goodbye";
    System.out.println("With CharSequence: " + s.replace("Hello", testC));
  }
}

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This results in the following output:

Original String: Hello World!
With primitive char: Heeeo Wored!
With Character class: Hello oorld!
With CharSequence: Goodbye World!

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