String object

> . Strings are immutable.But String s="Hello"; String

> s1=s+"World"; S.O.P(s1); means printing "HelloWorld".

> How ?

Here, s1 and s are two different String objects. That is the reason it prints 'HelloWorld'.

Even when you say, s = s + "World"; the initial s is destroyed and a new s is created which will have the value 'HelloWorld'.

Phenoma at 2007-7-8 22:51:25 >

> Strings are immutable.But> String s1="Hello";

> s1=s1+"World";

> System.out.println(s1);

> means printing "HelloWorld". How ?

Strings are immutable.

String references are mutable (unless declared final).

Your example uses two String literals from the constant pool.

These Strings are added to the String pool.

These Strings are immutable.

You concatenate them creating a new String.

The new String is added to the String pool.

The new String is immutable.

Your String reference "s1" is mutable.

tschodta at 2007-7-8 22:51:25 >

> embla now tell me what will happen to string object

> "hello''.now where it will be stored .s1 indicates

> new string object."hello" will be garbage collected

> or it is still in the memory

String is not an ordinary class. It has so called "special language support" so it behaves kind of odd compared with other classes.

A String literal like "hello" will be stored in the string literal pool the first time it's used in a program. After that one object will be allocated representing "hello" and stored on the heap. This object will never be GC'ed and it will always represent the "hello" string literal during the program. This is why if you do,

String s1 = "hello";

String s2 = "hello";

S1 and s2 will hold the same object reference namely the one representing the "hello" literal. If you instead do

String s3 = new String("hello");

S3 will differ from s1 and s2. It's because the new operator always creates a new object but this object still will use the "hello" literal stored in the string literal pool.

The object which s3 holds a reference to can be GC'ed but never the object s1 and s2 references. This object stays. It's associated with the "hello" literal during the whole program.

namita.pradhan08a at 2007-7-8 22:51:25 >