String question

[Bin Wang]

System.out.println("string" == "string"); //output: true
System.out.println("string".toString() == "string"); //output: true
System.out.println(" string ".trim() == "string"); //output: false
So " string ".trim() returns a new String instance of "string" which is not the literal String instance "string"?

[Terence Doyle]

Hi,
" string ".trim() constructs and returns a new string so the reference is not the same anymore ie. its a new object.
You would get true in you used an equals() call instead in the 3rd line because its looking for the same value.

Bye,
Terry

[Kevin Yip]

Since String objects are immutable, every method that tries to manipulate them will return a new String object.
The implementation of the toString() method in the String class is a little special: it does not try to manipulate the String object, it just return the same object.
FYI, the implementation is :

public String toString()
{
   return this;
}

[Bin Wang]

Kevin,
Another special case of String class as far as I know:
System.out.println("STRING".toUpperCase() == "STRING");//true

[Vani Kadur]

Hi,
The trim() method returns the reference to the same object if it does not need to be modified, that is it has no leading and trailing blanks. If the original String object needs to be changed then a reference to a new String object is returned.
Hope this helps.
Vani

[Haining Mu]

you can find similar questions about string in
http://www.angelfire.com/or/abhilash/Main.html

[Sandeep Nachane]

You may also want to try this
http://www.tipsmart.com/studytools/selfreview/objequiv.htm
-Sandeep