Enthuware

Isn't Integer mutable if the value lies between -128 and 127. And so the increment here will acutally affect the Integer variable?

No, none of the wrapper classes is mutable.
I think you are confusing interning with mutability. Integer objects for integers between -128 to 127 are interened. I.e. if you have the following two lines:
Integer i1 = 100;
Integer i2 = 100;
then i1 and i2 would be referring to the same Integer object.

HTH,
Paul.

Thanks Paul!

public class TestClass{
public static Integer wiggler(Integer x){
Integer y = x + 10;
x++;
System.out.println(x);
return y;
}

public static void main(String[] args){
Integer dataWrapper = new Integer(5);
Integer value = wiggler(dataWrapper);
System.out.println(dataWrapper+value);
}
}

here the o/p: 6,20 so q is how 6 is coming since wrappers are immutable.