15

I have a string:

String c = "IceCream";

If I use toUpperCase() function then it returns the same string, but I want to get "ICECREAM".

Where is the problem?

Sergey Kalinichenko
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user1091510
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5 Answers5

34

The code

String c = "IceCream";
String upper = c.toUpperCase();
System.out.println(upper);

correctly prints "ICECREAM". However, the original string c isn't changed. Strings in Java are immutable so all operations on the string return a new copy.

Andreas Wederbrand
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  • See also http://stackoverflow.com/questions/22397861/why-is-string-immutable-in-java – Raedwald Jul 21 '14 at 13:08
  • You could also just reassign the variable **String c = "IceCream"; c = c.toUpperCase();** This should be included in the accepted answer. – ViaTech Apr 29 '18 at 16:07
13

Are you expecting the original variable, c, to have been changed by toUpperCase()? Strings are immutable; methods such as .toUpperCase() return new strings, leaving the original un-modified: 

String c = "IceCream";
String d = c.toUpperCase();
System.out.println(c); // prints IceCream
System.out.println(d); // prints ICECREAM
Shantha Kumara
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smendola
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10

The object can't be changed, because String is immutable. However, you can have the reference point to a new instance, which is all uppercase:

String c = "IceCream";
c = c.toUpperCase();
Xaerxess
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Zohaib
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3

You're supposed to use it like this:

String c = "IceCream";
String upper_c = c.toUpperCase();
Luchian Grigore
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1

It could be a problem with your locale. Try:

String c = "IceCream";
return c.toUpperCase(Locale.ENGLISH);
Zwade
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