How many String objects in this code?

[Jaydeep Wagh]

Hello all, I am preparing for the Sun Certification of Java and I have a question about the String class in Java.

#1 String s1="abc";
#2 String s2="def";
#3 System.out.println(s1 + " " + s2);

my question is that in the above code how many objects are created after the line #3 executes...?

Please do provide your explanation as well. Thanks in advance.

[Matthew Brown]

Please don't post the same question to multiple forums. I've deleted the other one.

[howie jao]

It created two string objects. If s2 = "abc" , it would just create one object because of string literal pool

[Matthew Brown]

howie jao wrote:It created two string objects. If s2 = "abc" , it would just create one object because of string literal pool

But what about line 3?

[Mohamed Sanaulla]

This is one of the most famous String related question asked on JavaRanch. Do read this article for more information

[fred rosenberger]

i'm not sure if the compiler can optimize this away or not.

Assuming it doesn't, I'd say five.

[Mohamed Sanaulla]

fred rosenberger wrote:i'm not sure if the compiler can optimize this away or not.

Assuming it doesn't, I'd say five.

5? Is it not 4? or each concatenation creates one string? that way it becomes 5.

[fred rosenberger]

I believe that each concatenation creates a new one. I am not sure, and some older, wiser (or even a younger, wiser) person may come along and tell me I'm wrong, so don't quote me.

[Suhas Mandrawadkar]

I m too confused now.

(abc) (def) (" ") (abc ) (abc def) <- 5 (I think this is right )

OR

(abc) (def) (abc ) (abc def) <- 4

[Nick Sher]

Jaydeep Wagh wrote: Hello all, I am preparing for the Sun Certification of Java and I have a question about the String class in Java.

#1 String s1="abc";
#2 String s2="def";
#3 System.out.println(s1 + " " + s2);

my question is that in the above code how many objects are created after the line #3 executes...?

Please do provide your explanation as well. Thanks in advance.

Creates 4 strings:
1. "abc"
2. "def"
3. " "
4. "abc def"

[Sunny Bhandari]

Why don't you guys use a de-compiler to see what does java compiler do to your code before generating the .class file.

Here is the de-compiled code for Hotspot. (the de-compiled code be different if the same code is compiled using different JVM like JRockit)

string s1 = "abc";
string s2 = "def";
system.out.println((new StringBuilder(string.valueOf(s1))).append(" ").append(s2).toString());

This clearly tells me that 4 String objects (abc, def, " " , abc def) and 1 String Builder (abc def) objects are created.

[Jaydeep Wagh]

@Mohamed Sanaulla : Thanks buddy, the article was really good and helped me understand some of the underlying stuff of Strings in Java....!

@all : even I also considered that the no. of objects created at line #3 is 4 as replied by Nick Sher.
anyway thanks for the help.

I will consult all you experts in case I need any further help.