Can anyone explain me what is state and mutable data?

In computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data.

http://en.wikipedia.org/wiki/Functional_programming

Can anyone explain me what is state and mutable data? Can anyone give me examples in either JAVA or JavaScript.

Answer

mutable suggest anything that can change, i.e. an int

int a = 0;
System.out.prtinln(a); //prints 0
a = 2;
System.out.prtinln(a); //now prints 2, so its mutable

In java a string is immutable. you cannot change the string value only its reference.

String s1 = "Hello";
System.out.println(s1); //prints Hello
String s2 = s1;
s1 = "Hi";
System.out.println(s2); //prints "Hello" and not "Hi"

State is something which an instance of a class will have (an Object).

If an Object has certain values for its attributes its in a diffrent state then another Object of the same class with diffrent attribute values