How to Convert a Java String from Uppercase with Underscores to CamelCase?

How can I transform a Java string from all uppercase with underscores to CamelCase?

String input = "THIS_IS_AN_EXAMPLE_STRING";

Converting a Java string from uppercase with underscores to CamelCase involves replacing underscores with empty strings and capitalizing the letters that follow them. This can be achieved efficiently using regular expressions in conjunction with Java string methods.

String input = "THIS_IS_AN_EXAMPLE_STRING";
String camelCaseString = input.toLowerCase()
                     .replaceAll("(?:^|_)(\w)", match -> match.group(1).toUpperCase());
System.out.println(camelCaseString); // Outputs: ThisIsAnExampleString

Causes

• The string is initially in uppercase with underscores separating the words.
• We need to create a format where each word starts with an uppercase letter and there are no separators.

Solutions

• Use `String.replaceAll()` to find underscores and the subsequent character, and replace them with the uppercase version of that character.
• Alternatively, use `String.split()` to divide the string and then manually construct the CamelCase result.

Mistake: Forgetting to handle the first word which does not follow an underscore.

Solution: Ensure to convert the first letter of the string after transforming the string to lower case.

Mistake: Not using the right regex pattern to match underscores and capitalize correctly.

Solution: Double-check the regex and use proper capturing groups in your replacement.