How is possible to apply toUpperCase() on an empty String in Java?

java string language-concepts
GniruT picture GniruT · Oct 10, 2015 · Viewed 8.1k times · Source

I've thought that if I run this

System.out.println("toUpperCase() on empty String:"+ "".toUpperCase());

and it returns an empty String. How is that possible? toUpperCase() should fail in this case isn't it? Thanks!

Answer

Eran picture Eran · Oct 10, 2015

Why should it fail? It converts any character of the input String to upper case. In your example, "any character" is equivalent to 0 characters.

The Javadoc doesn't say that it should fail for an empty String, which means it shouldn't fail :

Converts all of the characters in this String to upper case using the rules of the default locale. This method is equivalent to toUpperCase(Locale.getDefault()).

Note: This method is locale sensitive, and may produce unexpected results if used for strings that are intended to be interpreted locale independently. Examples are programming language identifiers, protocol keys, and HTML tags. For instance, "title".toUpperCase() in a Turkish locale returns "T\u0130TLE", where '\u0130' is the LATIN CAPITAL LETTER I WITH DOT ABOVE character. To obtain correct results for locale insensitive strings, use toUpperCase(Locale.ENGLISH).

Returns: the String, converted to uppercase.

Related questions

How do I convert a String to an int in Java?

How can I convert a String to an int in Java? My String contains only numbers, and I want to return the number it represents. For example, given the string "1234" the result should be the number 1234.

Read More
How to split a string in Java

I have a string, "004-034556", that I want to split into two strings: string1="004"; string2="034556"; That means the first string will contain the characters before '-', and the second string will contain the characters after '-'. I also want to …

Read More
How do I compare strings in Java?

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug. Is == bad? When should it and should …

Read More