Convert a String to uppercase and lowercase in Java

This post will discuss how to convert a string to uppercase and lowercase in Java.

1. Using `toLowerCase()/toUpperCase()` method

The standard solution to convert all of the characters in a string to lower case is calling the toLowerCase() method. Since Strings are immutable in Java, this method will create a new instance of the string.

public class Main

{

public static void main(String[] args) {

String s = "Hi";

System.out.println(s.toLowerCase()); // hi

}

Download Run Code

It has an overloaded version that accepts a Locale. Its usage is demonstrated below. The code converts the String to lower case using the rules of the specified locale.

import java.util.Locale;

public class Main

{

public static void main(String[] args) {

String s = "Hi";

System.out.println(s.toLowerCase(Locale.ENGLISH)); // hi

}

Download Run Code

To convert a string to uppercase, the String class provides a similar method toUpperCase():

public class Main

{

public static void main(String[] args) {

String s = "hi";

System.out.println(s.toUpperCase()); // Hi

}

Download Run Code

Note: It is advisable to place a null-check before calling the toLowerCase() or toUpperCase() method to avoid NullPointerException.

2. Using `WordUtils` class

Another solution is to use the WordUtils class from Apache Commons Text. It provides the uncapitalize() method that uncapitalizes all the whitespace-separated words in a String. You should use this method if and only if you need to do lowercase of each word in a string.

import org.apache.commons.text.WordUtils;

public class Main

{

public static void main(String[] args) {

String s = "Hello World";

System.out.println(WordUtils.uncapitalize(s)); // hello world

}

Download Code

All methods in the WordUtils class handles null strings gracefully. To capitalize all the whitespace-separated words, use WordUtils.capitalizeFully() method. It converts each word in the string to a title case character, followed by all lowercase characters.

import org.apache.commons.text.WordUtils;

public class Main

{

public static void main(String[] args) {

String s = "hello world";

System.out.println(WordUtils.capitalizeFully(s)); // Hello World

}

Download Code

That’s all about converting a String to uppercase and lowercase in Java.

Convert a String to uppercase and lowercase in Java

1. Using toLowerCase()/toUpperCase() method

2. Using WordUtils class

Share this:

1. Using `toLowerCase()/toUpperCase()` method

2. Using `WordUtils` class