Rectangle.java

public class Rectangle{//class header
   //instance variables - data
   private int length, width;

   //Constructors
   //Default
   public Rectangle(){
      length = 0;
      width = 0;
   }

   //Specified
   public Rectangle(int l, int w){
      length = l;
      width = w;
   }

   //Getters/Accessors
   public int getLength(){
      return length;
   }

   public int getWidth(){
      return width;
   }

   //Setters/Mutators
   public void setLength( int l ){
      length = l;
   }

   public void setWidth( int w ){
      width = w;
   }

   //toString
   public String toString(){
      return "Length: " + length + "\nWidth: " + width;
   }

   //"special" methods

   //area
   public int area(){
      int theArea = length * width;
      return theArea;
   }

   //perimeter
   public int perimeter(){
      return 2 * length + 2 * width;
   }

   //diagonal
   public double diagonal(){
      return Math.sqrt( Math.pow( length, 2 ) + Math.pow( width, 2 ) );
   }
}