Thread: Using an array which is in a superclass

Ok so I have these two classes: Book and Encyclopedia. I want to create a method in Encyclopedia. I want it to modify an array which is an object in Book class. I'm not allowed to take the array as a method input like this: public void MethodName(Book [] a, String ...){ Instead, I have to find a way to call that array in the method and modify one of the elements in it. I know how to modify the element, just I don't know how to call the array in a superclass to a subclass. Thanks.

In order to directly edit a variable from a superclass, you need to set it protected. Here is the gist of the modifiers:

• public: Anyone can use the variable.
• no modifier: Anyone in this package can use this variable.
• protected: Sub-classes can use this variable
• private: Only this class can use this variable

So let's say you have a "Beverage" and a "Soda" class. Where Soda extends Beverage

Beverage:

/**
 * A classic beverage with a name. Not inheritantly mutable.
 */
public class Beverage
{
  //Variables
  /**
   * The name of the Beverage
   */
  protected String name;
  //Constructors
  /**
   * Specifies the name of the beverage.
   * @param nameOfBeverage The name of the beverage
   */
  public Beverage(String nameOfBeverage)
  {
    name = nameOfBeverage;
  }
  //Methods
  /**
   * @return name of the beverage
   */
  public String getName()
  {
    return name;
  }
}

Soda:

/**
 * Extension of Beverage whom's name is either Coke, Dr. Pepper, or Root Beer.
 */
public class Soda extends Beverage
{
  //Constructors
  /**
   * Create a beverage of the specified type. 0, 1 and 2 being Coke, Dr. Pepper and Root Beer respectively.
   */
  public Soda(int type)
  {
    /* First get the String value of the type.  I do believe it is only possible to call
     * the super-classes constructor as the first line of code, so we modifiy the variable
     * directly.
     */
    String name = null;
    switch(type)
    {
      case 0:
        name = "Coke";
        break;
      case 1:
        name = "Dr. Pepper";
        break;
      case 2:
        name = "Root Beer";
        break;
    }
    //Call our parent classes variable "name" and sets it.
    super.name = name;
  }
}