Why Java Character.toUpperCase/toLowerCase has no Locale parameter like String.toUpperCase/toLowerCase

Question

I am wondering that why Character.toUpperCase/toLowerCase has no Locale parameter like String.toUpperCase/toLowerCase.

I have to first uppercase of a text that can be in Any language. I have 2 solutions:

1. Use Character.toUpperCase

   String text = "stack overflow";
   StringBuilder sb = new StringBuilder(text);   
   
   sb.setCharAt(0, Character.toUpperCase(sb.charAt(0))); // No Locale parameter here.
   
   String out = sb.toString(); //Out: Stack overflow
   

2. Use String.toUpperCase

   Locale myLocale = new Locale(locateId);
   
   String text = "stack overflow";
   String text1 = text.substring(0,1).toUpperCase(myLocale );
   String text2 = text.substring(1);
   
   String out = text1 + text2; // Out: Stack overflow
   

For my Locale. Both way has the same result.

My question is:

• Since the text can be in any language. Which way should I use?

• Why Character.toUpperCase/toLowerCase has no Locale parameter because there is not much difference between Character.toUpperCase/toLowerCase and String.toUpperCase/toLowerCase because String is array of Characters.

Answer 1

As the Javadoc says:

In general, String.toUpperCase() should be used to map characters to uppercase. String case mapping methods have several benefits over Character case mapping methods. String case mapping methods can perform locale-sensitive mappings, context-sensitive mappings, and 1:M character mappings, whereas the Character case mapping methods cannot.

So use String.toUppercase()

Answer 2

From the Character#toUpperCase(int) Javadoc,

In general, String.toUpperCase() should be used to map characters to uppercase. String case mapping methods have several benefits over Character case mapping methods. String case mapping methods can perform locale-sensitive mappings, context-sensitive mappings, and 1:M character mappings, whereas the Character case mapping methods cannot.

So, the answer is your second example (String.toUpperCase)

Answer 3

Here I'll explain some of the issues involved with supporting a ToUpperCase and ToLowerCase version for chars, in addition to Strings, that a locale parameter would not solve:

1. It's possible for an upper- or lower-case version of a char to be a string spanning more than one char. An example is the German ß expanding to SS in its upper-case version.

2. A char is a 16-bit value, but not all Unicode characters (and not even all Unicode letters) can fit in a 16-bit char. Thus, a char version of ToUpperCase and ToLowerCase will not support the entire Unicode character repertoire.

3. Some case mapping conversions (such as the Greek sigma) depend on context; that is, what kinds of characters come before or after the character in question. A char version of ToUpperCase and ToLowerCase will not have this kind of context available.

Answer 4

If the question is "which method should I use", then this question is a duplicate of String conversion to Title Case and the correct answer is EITHER

• Apache Commons Lang StringUtils.captitalize() - Javadoc at http://commons.apache.org/proper/commons-lang/javadocs/api-2.5/org/apache/commons/lang/StringUtils.html
• Apache Commons Lang WordUtils.capitalize() - Javadoc at http://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/text/WordUtils.html. This capitalizes each individual word.

If the question is "why doesn't Character have locale-sensitive case-changing methods", then the only way you're likely to get an answer is to consult one of the designers of the Java language. It's unlikely that the Stack Overflow community will be able to give you the answer you want.