Most efficient way to make the first character of a String lower case?

Question

Given an input String, what is the most efficient way to make just the first character lower case?

I can think of a number of ways to do this. For example, using charAt and subString:

String string= "SomeInputString";
string = Character.toLowerCase(
  string.charAt(0)) + (string.length() > 1 ? string.substring(1) : "");

Or using a char array:

 String string= "SomeInputString";
 char c[] = string.toCharArray();
 c[0] = Character.toLowerCase(c[0]);
 string = new String( c );

I am about to run some tests for the above examples, but I am sure there are many other ways to achieve this effect. What do you recommend?

Answer 1

Strings in Java are immutable, so either way a new string will be created.

Your first example will probably be slightly more efficient because it only needs to create a new string and not a temporary character array.

Answer 2

How about adding 32 to the char (as int):

String string= "SomeInputString";
string = (string[0] + 32) 
+ (string.length() > 1 ? string.substring(1) : "");

That way you avoid the function call.

Answer 3

When it comes to string manipulation take a look to Jakarta Commons Lang StringUtils

Answer 4

Despite a char oriented approach I would suggest a String oriented solution. String.toLowerCase is Locale specific, so I would take this issue into account. String.toLowerCase is to prefer for lower-caseing according to Character.toLowerCase. Also a char oriented solution is not full unicode compatible, because Character.toLowerCase cannot handle supplementary characters.

public static final String uncapitalize(final String originalStr,
            final Locale locale) {
        final int splitIndex = 1;
        final String result;
        if (originalStr.isEmpty()) {
        result = originalStr;
        } else {
        final String first = originalStr.substring(0, splitIndex).toLowerCase(
                locale);
        final String rest = originalStr.substring(splitIndex);
        final StringBuilder uncapStr = new StringBuilder(first).append(rest);
        result = uncapStr.toString();
        }
        return result;
    }

UPDATE: As an example how important the locale setting is let us lowercase I in turkish and german:

System.out.println(uncapitalize("I", new Locale("TR","tr")));
System.out.println(uncapitalize("I", new Locale("DE","de")));

will output two different results:

ı

i