Why can't I do assignment outside a method?

Question

If I try to assign a value to a variable in a class, but outside a method I get an error.

class one{
 Integer b;
 b=Integer.valueOf(2);
}

b

Answer 1

Methods have the responsibility to perform mutations on the member variables. If the member variable needs to be initialized, java provides a way to do it during construction, class definition (latter case). But the mutation cannot be performed during definition.(former case). It is usually done at the method level.

Objects are meant to hold the state, while methods are meant to operate on that state.