Object assignment in java

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4.00/5 (1 vote)

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Hi all,

I have a class Test.
Test t1 = new Test();
Test t2 = new Test();
t2 = t1;
I know any change in t1 will affect t2. Please tell me what is the reason for that?

Posted 22-Jun-11 20:49pm

Silju MC

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[no name] 23-Jun-11 2:50am

what exactly you want to know. Please explain

3 solutions

Solution 1

Because Object is of reference type. Which refer to the memory pointer.

When you assign t1 in t2. t2 and t1 hold the same pointer (memory address ref). and when we change t1 value t2 will automatically get changed.

Posted 22-Jun-11 20:54pm

2irfanshaikh

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Manfred Rudolf Bihy · Accepted Answer · 2011-06-22T21:00:00

Solution 3

The reason is quite simple: After t2=t1 both variables hold a reference to one and the same instance of class Test. The object created and assigned to t2 is no longer referenced anywhere and can garbage collected.

Cheers!

--MRB

Posted 22-Jun-11 21:00pm

Manfred Rudolf Bihy

Updated 22-Jun-11 21:02pm

v2

Comments

Silju MC 23-Jun-11 3:34am

Thanks for your answer. I think this is the correct one.
Suppose the case of String. See bellow

String s1="Hello";
String s2="World";
s1=s2;

In this case, What happened in String pool??

Thanks in Advance

Manfred Rudolf Bihy 23-Jun-11 5:30am

Strings are objects like very much everything in .net so the same applies as in your example. There is a slight difference though for strings. As they are immutable assigning a string literal twice to different variables will still produce only one instance. As all objects strings too can get garbage collected when they are no longer referenced.

Prerak Patel · Accepted Answer · 2011-06-22T20:55:00

Solution 2

Before assignment

t1 -----> Memory for t1
t2 -----> Memory for t2

When you assign t1 to t2, reference of t1 is passed to t2.

t1 -----> Memory for t1
t2 ---|

So, both the variables point to same object.
Change to any of them will be reflected in both.

Posted 22-Jun-11 20:55pm

Prerak Patel

Updated 22-Jun-11 20:57pm

v3

Comments

Sergey Alexandrovich Kryukov 23-Jun-11 4:11am

Nice way to explain, my 5.
--SA

Prerak Patel 23-Jun-11 4:12am

Thank you SA...

Silju MC 23-Jun-11 4:45am

:-) Thanks

Prerak Patel 23-Jun-11 4:45am

Welcome.

Silju MC 24-Jun-11 1:05am

hiI really like your way of explanation... thank you once again and my 5... cheers... :-)