In this tutorial, we will explore how to capitalize the first letter of a string in Java. This is a common requirement in many applications, such as formatting user input or generating text for display.
To achieve this, we can use a combination of Java’s built-in string methods. The most straightforward approach involves using the substring() method to extract the first character and the toUpperCase() method to convert it to uppercase. We then concatenate this with the rest of the string, which remains unchanged.
Here is an example:
String original = "hello";
String capitalized = original.substring(0, 1).toUpperCase() + original.substring(1);
System.out.println(capitalized); // Output: Hello
In this code:
original.substring(0, 1)extracts the first character of the string.toUpperCase()converts this character to uppercase.original.substring(1)gets the rest of the string (from index 1 to the end).- We concatenate these two parts together using the
+operator.
If you want to ensure that only the first letter is capitalized and the rest remains in lowercase, you can use the following approach:
String original = "hELLO";
String capitalized = original.substring(0, 1).toUpperCase() + original.substring(1).toLowerCase();
System.out.println(capitalized); // Output: Hello
In this modified version:
original.substring(1).toLowerCase()converts the rest of the string (after the first character) to lowercase.
Alternatively, you can use external libraries like Apache Commons Lang, which provides a convenient method called capitalize() in its StringUtils class. This method not only capitalizes the first letter but also handles edge cases such as null or empty strings:
import org.apache.commons.lang3.StringUtils;
String original = "hello";
String capitalized = StringUtils.capitalize(original);
System.out.println(capitalized); // Output: Hello
To use Apache Commons Lang, you need to include it in your project dependencies. If you’re using Maven, add the following dependency to your pom.xml:
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.12.0</version>
</dependency>
For Gradle, use:
implementation 'org.apache.commons:commons-lang3:3.12.0'
Another option for Spring framework users is the capitalize() method provided in org.springframework.util.StringUtils:
import org.springframework.util.StringUtils;
String original = "hello";
String capitalized = StringUtils.capitalize(original);
System.out.println(capitalized); // Output: Hello
When choosing between these methods, consider your project’s existing dependencies and whether you need to handle additional edge cases. The built-in Java approach is lightweight but requires manual handling of null or empty strings. External libraries like Apache Commons Lang offer more robust solutions with less code.
In conclusion, capitalizing the first letter of a string in Java can be achieved through various methods, ranging from simple string manipulation using substring() and toUpperCase(), to utilizing external libraries like Apache Commons Lang for more comprehensive handling.