String creation

when i write the statement

String s = new String("abc") ;

There are two string objects created right??

so in the code below how many string objects are actually created.

String s1 = "abc";
String s2 = new String("xyz");
s2=s1;
s1.toUpperCase();
String s3 = "abc" ;
String s4 = s3.replace('a','A');

well i think in all five objects are created.
please correct me if i am wrong.

Originally posted by Rohan Pujari:
...i think in all five objects are created...

That's my count.

2 at compile time------"abc" and "xyz"
3 at runtime-----------new,toUpperCase(),replace()

Not too sure if "xyz" is created at compile time.
when a string is created using the new operator, then an object is created on the heap (whose reference is returned) and another in the pool (which remains in the pool).

What if "xyz" was already in the pool, it wouldn't be created.
Actually now i am a little confused.
If any string literal is already in the pool it wouldn't be created, rite?

So how can we be sure abt the number of objects being created, unless we know that the string pool is empty?

if "abc" & "xyz" were already in the pool, we would have just 3 objects created or 4 if "abc" was ONLY in the pool, or 5 if none of them were in the pool.

Originally posted by swarna dasa:
...how can we be sure abt the number of objects being created, unless we know that the string pool is empty? ...

That's a good point. For questions like this, I think the underlying assumption is that we are starting with an empty String pool. Otherwise, we can't really answer the question.

this is the .class
----------------------------
class Screen {
public static void main(String[] args) {
String s1 = "abc";
String s2 = new String("xyz");

} }
---------------------------------

this is bytecode of Screen.class

---------------------------------
Compiled from "Screen.java"
class Screen extends java.lang.Object{
Screen();
Code:
0:aload_0
1:invokespecial#1; //Method java/lang/Object."<init>"

)V
4:return

public static void main(java.lang.String[]);
Code:
0:ldc#2; //String abc
2:astore_1
3:new#3; //class String
6:dup
7:ldc#4; //String xyz
9:invokespecial#5; //Method java/lang/String."<init>"

Ljava/lang/String

V
12:astore_2
13:return

}

-------------------------------------
see the line 3,7,9

3---create the instance of vlass String
7---push string xyz
9---this method <init>initial instance which make at line 3 to 5.

please correct me if required.