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String Immutable

Harshana Dias
Ranch Hand

Joined: Jun 11, 2007
Posts: 331

We know that Strings are immutable and if you want to change the original String value we have to use StringBuffer or StringBuilder class right?
But String class is final which make sense with immutability but why the StringBuffer and StringBuilder classes are also final?
Doesn't it have a impact on sting non immutability on those classes or it just make us not extend those classes?

Thank You.
Rok Štelcer
Ranch Hand

Joined: Nov 03, 2009
Posts: 101

StringBuffer and StringBuilder are more or less only "wrappers" for String, thus quite fundamental.
I guess that the only reason why they were made final is because of the security and performance.


Somnath Mallick
Ranch Hand

Joined: Mar 04, 2009
Posts: 482
But what about this:

Wouldn't this print:

Rob Spoor

Joined: Oct 27, 2005
Posts: 20279

That's just reassigning a different String object to the String reference. The String object itself cannot be changed.

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Campbell Ritchie

Joined: Oct 13, 2005
Posts: 46437
It might be better to think of String and StringBuilder as two different ways to handle the same data. One is for storage of immutable data and the other for manipulation of data we want to change. But both store "writing".
salvin francis
Ranch Hand

Joined: Jan 12, 2009
Posts: 1141

your statement is flawed:
We know that Strings are immutable and if you want to change the original String value we have to use...

Let me Quote my belief:

Strings are immutable and if you have the requirement to have an optimised approach towards using a
String with multiple operations of modifications being done on it, you would probably want to use a StringBuffer (or StringBuilder or MySomeWakyClassThatHandlesStringsWell)

By the way, a String is Not a StringBuffer


should not compile

I agree. Here's the better link:

subject: String Immutable
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