String replace() method in Java with Examples
The String replace() method returns a new string after replacing all the old characters/CharSequence with a given character/CharSequence.
Example:
Return a new string where all ” o” characters are replaced with “p” character:
Java
// Java program to demonstrate// the replace() methodpublic class Main { public static void main(String[] args) { // Define an original string String originalString = "Hello World"; // Replace 'o' with 'p' in the original string String replacedString = originalString.replace("o", "p"); // Print the replaced string System.out.println(replacedString); }} |
Output
Hellp Wprld
Syntax
public String replace(char oldch, char newch)
Parameters
- oldch: the old character.
- newch: the new character.
Return Value
- It returns a string derived from this string by replacing every occurrence of oldch with newch.
Exception
- NullPointerException- replace() method returns this exception when the target char/CharSequence is null.
Java String replace() Examples
The following examples demonstrate how to use the replace() method in Java:
Example 1: Java String replace(char old, char new) Method
To show the working of replace(char old, char new).
Java
// Java code to demonstrate the// working of replace()public class rep1 { public static void main(String args[]) { // Initialising String String Str = new String("Welcome to geeksforgeeks"); // Using replace to replace characters System.out.print("After replacing all o with T : "); System.out.println(Str.replace('o', 'T')); // Using replace to replace characters System.out.print("After replacing all e with D : "); System.out.println(Str.replace('e', 'D')); }} |
Output
After replacing all o with T : WelcTme tT geeksfTrgeeks After replacing all e with D : WDlcomD to gDDksforgDDks
Example 2: Java String replace(String target, String replacement) Method
We can implement the replace() method with substring/CharSequence just like with char.
To show the working of the replace(String target, String replacement) method.
Java
// Java Program to implement// replace() methodimport java.io.*;class GFG { public static void main(String[] args) { String s1 = "GeeksforGeeks"; // orignal string System.out.println(s1); // Replace Geeks with Gfg String replaceString = s1.replace("Geeks", "GfG "); // New String System.out.println(replaceString); }} |
Output
GeeksforGeeks GfG forGfG
Example 3:
The null regular expression is not accepted by the replace() method, it raises the NullPointerException.
Java
// Java Program to implement// Java replaceAll() methodimport java.io.*;// Driver Classclass GFG { // Main function public static void main(String[] args) { String str = "GeeksforGeeks"; int size = str.length(); System.out.println(str); String target = null; // replacing null with GFG str = str.replace(target, "GFG"); System.out.println(str); }} |
Output
Exception in thread "main" java.lang.NullPointerException
at java.base/java.lang.String.replace(String.java:2142)
at GFG.main(GFG.java:12)
String replace() Method – Java Programs
Let’s see some coding problems and solve them with the String charAt() method in Java.
1. Replace Substrings in a String Using the replace() Java method
Java
public class WordReplacement { public static void main(String[] args) { String sentence = "We are learning JavaScript"; String wordToReplace = "JavaScript"; String replacementWord = "Java"; System.out.println("Original sentence: " + sentence); String replacedSentence = replaceWord(sentence, wordToReplace, replacementWord); System.out.println("Replaced sentence: " + replacedSentence); } // Method to replace all occurrences of a word in a sentence private static String replaceWord(String sentence, String wordToReplace, String replacementWord) { // Use replaceAll() method to replace all occurrences return sentence.replaceAll("\\b" + wordToReplace + "\\b", replacementWord); }} |
Output
Original sentence: We are learning JavaScript Replaced sentence: We are learning Java
2. Replace Spaces with Underscores Using the replace() Java method
Java
public class ReplaceSpacesExample { public static void main(String[] args) { String sentence = "Geeks for Geeks"; String replacedSentence = replaceSpaces(sentence); System.out.println("Replaced sentence: " + replacedSentence); } // Method to replace spaces with underscores private static String replaceSpaces(String sentence) { return sentence.replace(" ", "_"); }} |
Output
Replaced sentence: Geeks_for_Geeks
References
To know more about more String Methods refer to the article Java String Methods
Whether you are a beginner starting Java programming or an experienced looking to brush up on your Java skills, this tutorial will provide you with a deep understanding of the replace function and its uses in Java.
The charAt method in Java is a fundamental function for string manipulation. With this guide, you can easily access the characters of a string using the replace function.
