String

[Vivek Shrivastava]

Please explain these questions, I really don�t understand
Q#1
Read this piece of code carefully
if("String".replace('T','t') == "String")
System.out.println("Equal");
else
System.out.println("Not Equal");
Answers
1. the code will compile an print "Equal".
2. the code will compile an print "Not Equal".
3. the code will cause a compiler error
Answer is 1.
Q#2
Read this piece of code carefully
if("String".replace('g','G') == "String".replace('g','G'))
System.out.println("Equal");
else
System.out.println("Not Equal");
Answers
1 the code will compile an print "Equal".
2. the code will compile an print "Not Equal".
3. the code will cause a compiler error
Answer is 2.

i would appreciate it.

[Greg Whelan]

The replace method of the String class will return the same string if no replacement occurs. Otherwise a newly constructed String is returned.
So in the first question, "String".replace('T', 't') will evaluate to be the original "String". The == test is then true because of the rule that only one string literal is shared amongst all literals with the same contents.
The second question demonstrates that if a replacement occurs, new strings are constructed. These newly constructed strings will always be unique.

[Milind Kulkarni]

Hi Vivek,
If the character oldChar does not occur in the character sequence represented by this String object, then a reference to this String object is returned. Otherwise, a new String object is created that represents a character sequence identical to the character sequence represented by this String object, except that every occurrence of oldChar is replaced by an occurrence of newChar.
In the example 1:
When String".replace('T','t') is evaluated, char �T� is not found so it returns the same reference and == evaluates as True. �Equal� will be displayed.
In the Example 2:
A new string object is created and old char �g� is replaced by �G� and == evaluates as False and �Not Equal� will be displayed.
Hope this helps !!
Regards,
Milind

[Vivek Shrivastava]

I really got the point.
Thanks for your time.
regards
vievk

[Adrian Ferreira]

Sorry but,
"only one string literal is shared amongst all literals with the same contents."
To me, it would be easy to understand if this rule were true also for Q#2. Since both Strings have the same contents, it isn�t an exception for the rule? When this rule is valid?
Thanks,
Adrian

[Greg Whelan]

Yes, the strings in Q2 have the same contents but they are not string literals. They are new strings (non-literals) that are constructed and then returned by the replace method.
There was some interesting discussion along the same lines here:
http://www.javaranch.com/ubb/Forum24/HTML/001463.html

[Adrian Ferreira]

Greg,
Great! Now it sounds better to me.
Thanks,
Adrian

[Hari]

Hoop!.

I got It, Thanks for your question.