Special case null stack solution for https://www.codurance.com/katalyst/stack

Stack.java

interface Stack {
  static Stack create(int size) {
    if (size < 0) throw new IllegalStackSizeException();
    if (size == 0) return new NullStack();
    return new BoundedStack(size);
  }
  
  void push(int element);
  boolean isEmpty();
  // Other operations...
}

class NullStack implements Stack {
  @Override public void push(int element) {
    throw new StackOverFlowException(); // 0 stack always overflows
  }

  @Override public boolean isEmpty() {
    return true; // 0 stack is always empty
  }
}

class BoundedStack implements Stack {
  @Override public void push(int element) {
    // push code
  }

  @Override public boolean isEmpty() {
    // empty check code
  }
}

For the special case of a null stack, if you are using a language which supports polymorphism, consider creating a base abstract Stack, a BoundedStack with your current implementation, and a NullStack with only the code required for the 0 case. Then provide a way to construct either derivate of the stack based on the size provided.