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IF statement ptoblem

Micheal Smith
Greenhorn

Joined: Apr 08, 2006
Posts: 4
hi

this is my first post on these forums hehe

I am a beginner in java.

These days I was trying out some multi-threading and I am going on quite well but I encountered one strange problem with, believe it or not, an if statement.

I have the following code snippet inside my Run() method:



I think at this point the program should display YES EQUALS but it is displaying:

t1s: l
thread: l

Therefore the problem is that if t1s and thread are the same why is it jumping to the else statement?

Thanks alot for your help
Micheal
Muhammad Saifuddin
Ranch Hand

Joined: Dec 06, 2005
Posts: 1321

try to change ur code with this..
i m not sure about it but may be ur problem is solve.. just try it..

code:


String t1s;


t1s = Thread.currentThread().getName().toString();

if (t1s.equals(Thread.currentThread().getName().toString()))
{
System.out.println("YES EQUALS");
}
else
{
System.out.println("t1s: "+t1s);
System.out.println("thread:"+Thread.currentThread().getName().toString());
}



[ April 08, 2006: Message edited by: saif uddin ]

Saifuddin..
[Blog][Linkedin] How To Ask Questions On JavaRanch My OpenSource
Micheal Smith
Greenhorn

Joined: Apr 08, 2006
Posts: 4
A REAL BI THANKS MY FRIEND!

YOU SOLVED MY PROBLEM.

but may I ask ... why didnt it work with == and it workd with .equals?

just for curiosity hehe
Muhammad Saifuddin
Ranch Hand

Joined: Dec 06, 2005
Posts: 1321

hi,

== this comparesion operator is not for String but for all
because there is a wounderful method to comparing a strings
whenever u compare 2 String values String.equals()



Regards
SAif uddin
[ July 25, 2006: Message edited by: saif uddin ]
fred rosenberger
lowercase baba
Bartender

Joined: Oct 02, 2003
Posts: 11479
    
  16

the == operator basically compares the value of the variables. tls is a REFERENCE to a string object. what it holds is basically the memory address of where that String is.

the way your code was originally written, you created two distinct Strings, at different places in memory.

Therefore, == returns false.

the equals() method checks the CONTENTS of the objects, to see if they are equivelant.

Note that when you write your own classes, you will have to override the default equals() method with one that makes sense for your class.


There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors
Jackie Davis
Greenhorn

Joined: Mar 04, 2006
Posts: 23
Thanks for the explanation! This has just solved my problem too
 
 
subject: IF statement ptoblem