what is the exact definition of "immutable"?

[Steven Zeng]

Here is a scjp question :
which of the following classes produce immutable object :
a java.lang.Double
b java.lang.StringBuffer(i know it is false)
c java.lang.Boolean
d java.lang.Math

[Mike Shn]

Immutable means, once created, the contained value can't be changed.
P.S Do you preparing to take the 310-025 exam?
[ June 12, 2002: Message edited by: Mike Shn ]

[Thiru Thangavelu]

I think the answer is Double and Boolean. Math class doesn't have any public constructors, so an instance can't be created.

[Akhilesh Varma]

all wrapper classes and the string class objects are immutable so ans is double and boolean

[Steven Zeng]

Thanks ,all .I agree at your answer .