Java - How to capitalize the first letter of a String

In this section, we will show you how to capitalize the first letter of a String.

In Java, we can use str.substring(0, 1).toUpperCase() + str.substring(1) to make the first letter of a String as a capital letter (uppercase letter)

String str = "java";
String cap = str.substring(0, 1).toUpperCase() + str.substring(1);
//cap = "Java"

or We can use Apache's common library StringUtils.capitalize(str) API to capitalize first letter of the String.

String str = "java";
String cap = StringUtils.capitalize(str);
//cap == "Java"

1. str.substring(0,1).toUpperCase() + str.substring(1)

A complete Java example to capitalize the first letter of a String.

public class Main {

    public static void main(String[] args) {
        
        System.out.println(capitalize("knowledgefactory"));   // Knowledgefactory
        System.out.println(capitalize("java"));        // Java

    }

    // with some null and length checking
    public static final String capitalize(String str) {

        if (str == null || str.length() == 0)
        {
            return str;
        }
        //converts first char to uppercase and adds the remainder of the original string
        return str.substring(0, 1).toUpperCase() + str.substring(1);

    }
}

Console Output:

Knowledgefactory
Java

2. Using Apache Commons Lang 3, StringUtils.capitalize(str) method

We can use the Apache commons-lang3 library, StringUtils.capitalize(str) API to capitalize the first letter of a String in Java.

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

import org.apache.commons.lang3.StringUtils;

public class Main {

    public static void main(String[] args) {

        String str = "java";
        String cap = StringUtils.capitalize(str);
        System.out.println(cap);
    }
}