String Vs String Buffer

[shiva .B krishna]

Why is it that String immutable & String buffer mutable???

[bnkiran kumar]

Shiva, String immutable means if we create an objec of string with some value, the value is final we cannot change its value.

where as for string buffer, we can change the value present in string buffer object.
like StringBuffer b=new StringBuffer("kiran");
b.append("kumar");
now b will has kirankumar, we are able to change the content of
stringbuffer but where as for string, String str=new String("kiran");
str will always has content "kiran" even after this method call str.replace('i','r'); not only replace ,it is same for any other method .

[tapan hoskeri]

shiva,
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[shiva .B krishna]

Hi Kiran thanks for the reply. The explanation u gave at mutable & immutable is fine But then i was asked in an interview why is String made immutable & String buffer mutable.So pls try to answer that "why"

[bnkiran kumar]

Hi Siva,

String class is generally used when we require constant strings, StringBuffer is generally used if we want frequent operations(like append,delete etc) on the string.
may be they have done for compiler optimization, because there is no need to create a new object if we use constant strings.
StringBuffer was created because if we use strings which change frequently everytime a new object is created if we perform any operation on it.
May be experts like moderators of this form can answer this.