Java – Capitalize the first letter of a String

By Atul Rai | Last Updated: April 15, 2022 Previous       Next

In this short tutorial, you will get an idea of how to capitalize the first letter of a string. In Java, it can be possible in many ways like using core Java programming or using any third-party library e.g. Apache Commons Lang 3.

Similar Post: Capitalize the first letter of each word in a String using Java

1. Java 8 Lambda Expression

Java 8 introduced the Supplier<T> functional interface to implement the lambda expression in Java.

final String cityName = "new Delhi";
Supplier<String> str = () -> cityName.substring(0, 1).toUpperCase() + cityName.substring(1);

System.out.println(str.get()); // New Delhi

2. Core Java Programming

With Core Java programming, it will just increase the number of lines in your codebase, and the logic will remain the same as Java 8 Lambda Expression.

package org.websparrow;

import java.util.function.Supplier;

public class CapitalizeFirstLetter {

    public static void main(String[] args) {

        final String cityName1 = capitalizeFirstLetter("varanasi");
        System.out.println(cityName1); // Varanasi

        final String cityName2 = capitalizeFirstLetter("VARANASI");
        System.out.println(cityName2); // VARANASI

        final String cityName3 = capitalizeFirstLetter("$varanasi");
        System.out.println(cityName3); // $varanasi

    }


    public static String capitalizeFirstLetter(final String str) {

        if (null == str || str.trim().equals("")) {
            throw new RuntimeException("String is not valid");
        }
        return str.substring(0, 1).toUpperCase().concat(str.substring(1));
    }
}

Output:

Varanasi
VARANASI
$varanasi

3. Apache Commons Lang 3

With Apache Commons Lang 3 library, you can use its StringUtils.capitalize(String str) API to capitalize the first letter of a string. You can grab the Apache commons-lang3 by adding the below dependency to your pom.xml file.

<dependencies>
   <dependency>
      <groupId>org.apache.commons</groupId>
      <artifactId>commons-lang3</artifactId>
      <version>3.12.0</version>
    </dependency>
</dependencies>

// Apache Commons Lang 3, StringUtils
final String name1 = StringUtils.capitalize("atul");
System.out.println(name1); // Atul

final String name2 = StringUtils.capitalize("atul rai");
System.out.println(name2); // Atul rai

final String name3 = StringUtils.capitalize("ATUL RAI");
System.out.println(name3); // ATUL RAI

final String name4 = StringUtils.capitalize("@atul rai");
System.out.println(name4); // @atul rai

In Apache commons-lang3 library, there is another WordUtils.capitalize(String str) API that capitalizes the first letter of each word of a string, but it is deprecated from the 3.6.0 version.

// Apache Commons Lang 3, WordUtils
final String foo = WordUtils.capitalize("cow");
System.out.println(foo); // Cow

final String boo = WordUtils.capitalize("i'm a holy cow.");
System.out.println(boo); // I'm A Holy Cow.

References

1. Interface Supplier<T>- Java 8
2. StringUtils- Apache Commons Lang 3
3. WordUtils- Apache Commons Lang 3
4. How to capitalize the first letter of a String in PHP