0

My doubt is when I run the following program

public class NonStatic
{
  class a
  {
    static  int b;
  }
}

The compiler is giving a error that "inner classes cannot have static declarations"

ok,then I made a change instead of "static int b" to "final static int b" its giving

same error but when I wrote "final static int b=10" means with initialization compiler

didn't complain,please can any body explain this what's the concept behind this.

Improve this question
0

5 Answers 5

Reset to default
3

it is so by design, just see the Java Language Specification: Inner Classes and Enclosing Instances

An inner class is a nested class that is not explicitly or implicitly declared static. [...] Inner classes may not declare static members, unless they are compile-time constant fields (§15.28).

Improve this answer
Sign up to request clarification or add additional context in comments.

Comments

1

final static int b=10 Is interpreted as a constant so compiler can just inline it. Similarly you can have static final constants in interface.

final static int b Is missing initialization,which is required for final member, so compiler can't quite figure what you want. Try putting following block right after it out of curiosity:

static {
  b=10;
}

Although it probably would not work...

Improve this answer

2 Comments

yes its not working..if we wrap the inner class inside the interface it will work
@yagnya: wrapping in an interface will work, because nested interfaces are always static and all classes defined inside interfaces are static as well. So you've effectively found a complicated way to add the static keyword to your class definition.
1

If a field is static, there is only one copy for the entire class, rather than one copy for each instance of the class
A final field is like a constant: once it has been given a value, it cannot be assigned to again. hence when we r using final we have to assign the value to the variable.
have a look at the following link

Improve this answer

Comments

0

Here is my take on this issue.

  1. Inner class is defined as a not static member of outer class and hence, it's instance cannot exist without the instance of outer class.
  2. The static fields of a class are accessible without creating an instance of that class.
  3. Now if you add a static field in the inner class, that means you can access that field without create the instance of inner class BUT according to #1 instance of inner cannot exist without an instance of outer class. So this is the conflict and hence the error.

TO CROSSCHECK : Just declare the inner class static and it will correct the error.

Improve this answer

2 Comments

thanks santosh,then why its working for static int b=10; according to concept it should not?
@yagnya: 'static int b=10' will give compile error. only 'final static int b=10' will work which is as good as any constant.
0

Its because a final static variable is a constant meaning it can't change at run time, while a static variable is not a constant and can change during runtime.

So in a class static variables aren't allowed in an inner class but the constants(final) are allowed.

Improve this answer

Comments

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.