StringBuffer?

[Kitty Dayal]

Hi all,

I found this in one of the mock exam on the phil/simon book. Any anybody please explain the reasoning.

How many objects are created?
 
StringBuffer s1 = new StringBuffer ("abc");
StringBuffer s2 = s1;
StringBuffer s3 = new StringBuffer ("abc");
 

Answer given: 3

Should be not be 2. Since s2 is only a reference to the object created at s1?

Thanks
-Kits

[Barry Gaunt]

For passing the SCJP: the first object is the string "abc", the second object is the StringBuffer object constructed from "abc" and referenced by s1, and the third object is the StringBuffer object referenced by s3. This third object is constructed from the same "abc" as used to construct the first StringBuffer object.

As you correctly said, s2 is only a reference to the same object that s1 references, no new object is created.

[Vicky Jain]

Yups,

Three objects are created by this code, one string literal("abc") is created in the string pool and the other two string buffer objects are created on heap.

[Kitty Dayal]

Thanks Barry, Vivek

Will this one also create three objects?

String s = new String("abc");
String s1 = s;
String s2 = new String("abc");

One in the pool and two on heap.

Also I am not sure as to what kind of objects use string pool. (I thought only String class uses it).

Thanx,
-Kits

[Ravi Kotaru]

Yes. this code will also create 3 objects. one on the string pool and two on the heap