String Immutable

[Harshana Dias]

Hey,

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]

Hi,

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.


Regards,
Rok

[Somnath Mallick]

But what about this:

String abc = "ABC";
	abc = "DEF";
	System.out.println("String: " + abc);

Wouldn't this print:

String: DEF

[Rob Spoor]

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

[Campbell Ritchie]

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]

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

ie:

StringBuffer stringbuffer = new StringBuffer();
String myString=stringBuffer;

should not compile