EECS2030 Test 4

Programming question

Implement the Table class. A skeleton can be found here. The API can be found here. A jar with the Furniture and Leg classes can be found here.

• You have to put your Table class in the test4 package.
• You have to implement inheritance and composition.

package test4;

import java.util.HashSet;
import java.util.Set;

/**
 * A table is a piece of furniture.  Each table
 * has a collection of legs.  The table and its collection
 * of legs form a composition.
 */
public class Table extends Furniture implements Comparable<Table>
{
    private Set<Leg> legs;

    /**
     * Initializes this table with the given brand and the
     * given collection of legs.
     *
     * @param brand the brand of the table.
     * @pre. brand != null
     * @param legs the legs of the table.
     * @pre. legs != null
     */
    public Table(String brand, Set<Leg> legs)
	{
	    super(brand);
	    this.setLegs(legs);
	}
    
    /**
     * Returns the legs of this table.
     * 
     * @return the legs of this table.
     */
    public Set<Leg> getLegs() 
    {
	return new HashSet<Leg>(this.legs);
    }

    /**
     * Sets the legs of this table to the given collection of legs.
     * 
     * @param legs the legs of this table.
     * @pre. legs != null
     */
    public void setLegs(Set<Leg> legs) 
    {
	this.legs = new HashSet<Leg>(legs);
    }

    /**
     * Tests for equality of this table and the given other object.
     * Two tables are equal if they have the same brand and the
     * same number of legs.
     *
     * @param object Another object.
     * @return true if this table and the other are the same, false otherwise.
     */
    public boolean equals(Object object)
    {
	boolean equal;
        if (object != null && this.getClass() == object.getClass())
	{
	    Table other = (Table) object;
	    equal = super.equals(other) &&
	        this.getLegs().size() == other.getLegs().size();
	}
        else
	{
	    equal = false;
	}
        return equal;
    }

    /**
     * Compares this table with the given table.
     * This table is smaller than the other table if its unique id
     * is smaller than the unique id of the other table.
     *
     * @param other Another table.
     * @return (unique id of this table) -  (unique id of other table).
     * @throws NullPointerException if other is null.
     */
    public int compareTo(Table other)
    {
        return Integer.parseInt(this.toString()) - Integer.parseInt(other.toString());
    }
}

Other questions

public class CreditCard
{
   private double balance;

   /**
    * Checks if the balance of this card is positive.
    *
    * @throws Exception if the balance of this card is not positive.
    */
   public void checkPositive() throws Exception
   {
      if (this.balance <= 0)
      {
         throw new Exception("Balance is negative");
      }
   }
}

public class RewardCard extends CreditCard
{
   private int points;

   /**
    * Checks if the points balance of this card is positive.
    *
    * @throws Exception if the points balance of this card is not positive.
    */
   public void checkPositive() throws Exception
   {
      if (this.points <= 0)
      {
         throw new Exception("Points balance is negative");
      }
   }
}