Strings and mutablelity

[Dan Hansen]

Will all of these cause a new string object to be made?

String name = �Dan�;
name = name + � Hansen�;
name = name.substring(3, 5);
name = name.toUpperCase();

Or how many of them will?

[Joe San]

Dan you are right. All of them will create a new String on the heap.

[Sanjeev Singh]

However the methods substring and toUpperCase will not made the new String always.

String name = "DAN";
name = name + " HANSON";
name = name.substring(0, name.length()); //No new object will be created
name = name.toUpperCase(); // No new object creation

[Dan Hansen]

Originally posted by Sanjeev Kumar Singh:
However the methods substring and toUpperCase will not made the new String always.

 
name = name.substring(0, name.length()); //No new object will be created
name = name.toUpperCase(); // No new object creation

Could you please explain why?

[Pinkal Patel]

"Dan Hansen"
String is allready Created and Avilable in the Pool
So it just gave Ref. of it not new Object.

[Dan Hansen]

So "Dan Hansen" and "DAN HANSEN" is considered to be equal?

[Sanjeev Singh]

Dan wrote...
Could you please explain why?

These two methods return the this object if it operation has no effect on the object on which it was invoked.
Please look into the API for more details.

[y mashalkar]

This is in reference to this article

here's the code...
class A
{

public static void main(String[] args)
{

String one = "hey";
String two = new String("hey");

one = two = null;

String three = new String();
//String three = new String("hey");
three.intern();

System.out.println("value="+three);

}
}
this prints "value="..

second part...

class A
{

public static void main(String[] args)
{

String one = "hey";
String two = new String("hey");

one = two = null;

//String three = new String();
String three = new String("hey");
three.intern();

System.out.println("value="+three);

}
}
this prints "value=hey"....

The article mentions that even if references to String Literal & String Object are assigned to null..the String Literal Pool still has a reference to the String literal on the heap making it noneligible for garbage collection..ever!
it says.."You can reuse String Literals with run-time Strings by utilizing the intern() method."

How can one reuse the above literal?or rather how would it be beneficial to reuse it?whats the advantage of letting a resource occupy memory eternally?
as it would help only if the string content was same?
Can anybody explain?
Thnx

[Jim Yingst]

[Dan Hansen]: So "Dan Hansen" and "DAN HANSEN" is considered to be equal?

No one said anything like that. The point was that IF a string is already all uppercase, then toUpperCase() will not return a new string; it will simply return the same all-uppercase string it started with.