Answer in Memory point of view

Friends tell me what is the difference between in declaring,

String a =" abc "; and String b= new String("xyz");

when we apply "==" and "equals()" on first string , it depicts they are equal. but it is not in the case of second string. why it is so ? plz answer in memory point of view ?

Hi Santh Kumar,

Please,can u make the question somewhat clear?
Is it String b= new String("xyz") or String b= new String("abc");

What does it mean when you say "when we apply "==" and "equals()" on first string " ??

Thanks
Neelima

Hi Nelima ,

Just take four instance variables of type String .out of them two are similar

For Example,

String a=" 123 "; and String x=new String("456");
String b=" 123 "; and String y = new String("456");

when i compare 'a' and 'b' with "==" operator and "equals()" method , it returns "TRUE".

when i compare 'x' and 'y' with "==" operator , it returns "FALSE" and with "equals()" method ,it returns "TRUE" .

i checked these two on an IDE.

i though , there might some difference in creating Strings above said cases just initialization and with Object.

plz tell me the difference in creating the Strings .

with Regards,

santh kumar

When dealing with Strings in Java,we will be having actually two types of memory.
One is ---- Heap space
Another one -- Literal Pool

Case 1:
--------
So,here,when we say
String a = “abc”
The string literal is placed in literal pool referenced by ‘a’

Again,when we say
String b = “abc”
One more string object will not be created as the string literal is same,but the no. of references it is being referenced will be increased by one.So,now b also refers to the same literal on that pool.


Case 2:
--------
And, String x = new String(“xyz”)
This creates two objects,one on the heap and other on pool.

String y = new String(“xyz”);
This creates two more objects again.

This is how memory will be allocated for the above two cases.

And the difference between “ = = “ and “ equals “ is that
a) = = checks whether they are referring to the same object
b) equals checks whether the objects(ie., contents) are equal.

So,

a = = b is true as they are both referring to the same object
a.equals(b) is true as the object is same which is “abc”

x = = y is false as they are not referring to the same object
x.equals(y) is true as the content is same which is “xyz”.

Let me know if anywhere i am wrong.

Thanks
Neelima

Well Said Ms.Neelima .

Very sophisticated Answer. Hats off 2 U .

Thank u.

with regards,

santh