String prob. ...help

[ratul banji]

Hi all,
c the following code: ..............................//1
if(" String ".trim() == "String")
System.out.println("Equal");
else
System.out.println("Not Equal");

o/p : Not Equal

Now,c this code: ...............................//2
if( "String".endsWith(""))
Sytem.out.println("True");
else
System.out.println("False");
o/p : " True "
and , now this one: .............................//3

if( "String".startsWith(""))
Sytem.out.println("True");
else
System.out.println("False");
o/p The code produces : "True"
Now...my question is, if code 2 and 3 both produces "True" then how the output of the code 1 is "not Equal" !!
One can say ,it is because the code 1 is using String method and when a String method is used one new String is generated and return.
If u say this then explain me the following code :

if("String".concat("") == "String")
System.out.println("Equal");
else
System.out.println("Not Equal");
o/p : Equal

Hmmmm..I think my brain is not working properly...CAN SOME1 HELP ME ,,,

HELP !! HELP !! HELP !!

Regds.
<marquee> Ratul Banerjee </marquee>

[Pawan Kumar]

code 1:
if(" String ".trim() == "String")
System.out.println("Equal");
else
System.out.println("Not Equal");
o/p : Not Equal
If u say this then explain me the following code :
code 2:
if("String".concat("") == "String")
System.out.println("Equal");
else
System.out.println("Not Equal");
o/p : Equal
as with concat() it will not return new string if spaces are passed as parameter.
if you say
if("String".concat("pk") == "String")
then it will return a new string "Stringpk" which is now having other reference,so there r not equal
pawan

[Angela Narain]

Originally posted by Pawan Kumar:
code 1:
if(" String ".trim() == "String")
System.out.println("Equal");
else
System.out.println("Not Equal");
o/p : Not Equal
If u say this then explain me the following code :
code 2:
if("String".concat("") == "String")
System.out.println("Equal");
else
System.out.println("Not Equal");
o/p : Equal
as with concat() it will not return new string if spaces are passed as parameter.
if you say
if("String".concat("pk") == "String")
then it will return a new string "Stringpk" which is now having other reference,so there r not equal
pawan

This can be better explained w.r.t. to concat() as :
If the length of the argument string is 0, then this String object is returned. Otherwise, a new String object is created
See the below code
Code //3
if("String".concat(" ") == "String")
System.out.println("Equal");
else
System.out.println("Not Equal");
o/p Not Equal

[Jane Griscti]

Hi Ratul,
If the method completes without actually doing anything the original reference is returned.
In your first example <code>" String ".trim()</code>, there were whitespaces to be removed; the <code>trim()</code> method had to create a new String in order to return <code>"String"</code>, as promised by it's contract.
In your last example, <code>"String".concat("")</code>, there was nothing for <code>concat()</code> to do; the original String did not have to be altered so it's reference was returned.
For more information, read the String class documentation in the API
Hope that helps.

------------------
Jane Griscti
Sun Certified Programmer for the Java� 2 Platform

[ratul banji]

Thanks all.
It is little bit clear now.