Strange answers about "Strings" by JAMIE JAWORSKI

[Fawad Khan]

Hi,
I have got confused by the answers to the exercise questions in the book of JAMIE JAWORSKI at the end of the chapter explaining Strings and String Buffer.
Q5- (page 218)
Which of the following methods cause the String object referenced by s to be changed ?
A- s.concat()
B- s.toUpperCase()
C- s.replace()
D- s.valueOf()
And the answer given is A & B. With the explanation that "The toUpperCase() and concat() change their associated String Objects.
While when i put them in codes and run, the original String is returned and that is not changed untill we assign like
s = s.concat()
What is the problem here ?

[Sivalingam Sivasuthan]

Fawad Khan,
The answer is wrong String Objects are immutable So no methods can modify the String Objects.
Siva

[Graeme Brown]

I agree: concat, toUpperCase and replace all return new String objects. As do all the overloaded implementations of valueOf, but they are static methods, so have to be called by String.valueOf(primitive |Object )and not s.valueOf().

[Jane Griscti]

Hi Fawad,
Which book edition are you using? In the text I have, the question is:

5. Which of the following methods cause the String object referenced by s to be changed?
A. s.concat()
B. s.toUpperCase()
C. s.replace()
D. None of the above

And the correct answer given is:

D. String objects are immutable and cannot be changed.

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Jane Griscti
Sun Certified Programmer for the Java� 2 Platform

[Naveed Hassan]

Hi Jane
This question is from
1999 First Indain Edition
Naveed

[Jane Griscti]

Hi Naveed,
I've got the July 1999 Edition by New Riders Publishing.
Perhaps there's a type-0 in your edition ... I just checked his mock exam at http://www.jaworski.com/java/certification/ it uses the question I quoted with the correct answer as D. By coincidence it was the first question that popped up so I didn't have to dig! My lucky day
Hope that helps.
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Jane Griscti
Sun Certified Programmer for the Java� 2 Platform
[This message has been edited by Jane Griscti (edited February 23, 2001).]