The progrma gives o/p as "Not Equal" why?

[Ramesh Shanmugam]

if( "string".toUpperCase() == "STRING")
{
System.out.println("Equal");
}
else
{
System.out.println("Not Equal");
}

the O/p is "Not Equal". How is that?? can anyone explain me???

Thanks in advance
Ramesh

[Keith Lynn]

The method is creating a new String object containing STRING which is not the same object as "STRING".

Notice that this prints Equal.

public class Test14 {
 
   public static void main(String[] args) {
      if( "string".toUpperCase().intern() == "STRING") {
         System.out.println("Equal");
      } else {
         System.out.println("Not Equal");
      }
   }
 
}

[Joe Ess]

Because Strings are not primitive values which can be compared with "==". Strings are objects and in order to compare the contents of the object rather than the references to the object (which is what "==" does), one must use a method like equals() or compareTo().

[Ramesh Shanmugam]

Thanks for the replies

But this code gives an o/p as "equals"

if( "STRING".toUpperCase() == "STRING")
System.out.println("Equal");
else
System.out.println("Not Equal");

in this case, whether two objects refer to the same reference??
if so, how is that o/p??

Thanks in advance,
Ramesh

[Keith Lynn]

This is part of the implementation of toUpperCase(Locale).

scan: {
            char upperCaseChar;
            char c;
            for (firstLower = 0 ; firstLower < len ; firstLower++) {
                c = value[off+firstLower];
                upperCaseChar = Character.toUpperCaseEx(c);
                if (upperCaseChar == Character.CHAR_ERROR || c != upperCaseChar) {
                    break scan;
                }
            }
            return this;
        }

So basically the toUpperCase method checks first to see if there are any lowercase characters in the String. If there are, then it will create a new String. Otherwise, the method returns the same String.

The method toUpperCase() calls toUpperCase(Locale).
[ April 04, 2006: Message edited by: Keith Lynn ]

[Ramesh Shanmugam]

Thanks Keith Lynn ,

You explanation is very nice... Understood well

Thanks,
Ramesh