How many objects will be created in the string pool?

[Kaushik Baral]

If I have a code like this
String s1 = new String ("abc");
String s2 = "abc";
String s3 = "abc";

then how many objects will be created in the string pool?

[Rameshwar Soni]

2 Objects will be created.

[Kaushik Baral]

could you please explain how two objects will be created... thanks in advance

[Rameshwar Soni]

There are 2 ways to create String Objects in Java
(1) Using the new operator i.e.

String s1=new String("abc");

(2) Using the String Literal i.e.

String s2="abc";

.
.
Now String allocation is costly in both time and memory so the JVM(Java Virtual Machine) performs some tasks? WHAT TASKS?
See whenever you are using the "new" operator the object is created, JVM will not look in string pool it is just going to create the Object, but when you are
using the string literals for creating String objects then JVM will perform the task of looking in the string pool i.e.
When you will write

String s2="abc";

the JVM will look in string pool and check if "abc"already exists or not. If it exists then then a reference is returned
to the already existed string "abc" and new object is not created and if it doesn't exists then a object is created.
So in your case
(a)

String s1=new String("abc");

--------Since "new" is used to therefore Object is created
(b)

String s2="abc";

----using String literal a object is created and "abc" is not in string pool therefore Object is created
(c)

String s2="abc";

----Again using String literal and "abc" is in string pool therefore Object is not created.
.
.
You can also check it out by using the following the code

class String_Check
{
	public static void main(String[] n)
	{
		String s1=new String("abc");
		String s2="abc";
		String s3="abc";
		if(s1==s2)
			System.out.println("s1==s2");
		if(s1==s3)
			System.out.println("s1==s3");
		if(s2==s3)
			System.out.println("s2==s3");
	}
}

Hope this helps...Note == is used to see if Object are equal and equals(Object) method is used to see if content are equal.

[Rob Spoor]

Rameshwar Soni wrote:2 Objects will be created.

But only one in the String pool.

[Rameshwar Soni]

Yes its my mistake while replying to the question i had kept only "HOW MANY OBJECTS WILL BE CREATED" in my mind so i replied 2 Objects and the question was "HOW MANY OBJECTS IN STRING POOL" so it is ONE as Rob said and total 2 Objects.

[Kaushik Baral]

thanks everybody for your time. thing is clear now.

[Nam Ha]

Thanks Rameshwar Soni for your great explanation!
I got to understand String pool better now

[saloni jhanwar]

Rameshwar Soni wrote:
(a)

String s1=new String("abc");

--------Since "new" is used to therefore Object is created
(b)

String s2="abc";

----using String literal a object is created and "abc" is not in string pool therefore Object is created

String s2="abc"; won't create any object in literal pool because first statement String s1=new String("abc") creates two objects first on heap second on pool, so because of there is already "abc" literal is provided so second statement wont create any object again,s2 will just refer the second object in pool.

[Campbell Ritchie]

saloni jhanwar wrote: . . .
String s2="abc"; won't create any object in literal pool because first statement String s1=new String("abc") creates two objects first on heap second on pool, so because of there is already "abc" literal is provided so second statement wont create any object again,s2 will just refer the second object in pool.

“second object in pool” is confusing. Do you mean that the second variable will refer to the same object in the String pool?