public abstract class Employee implements Comparable
{
   //Class Constants
   public static final double MINIMUM_WAGE = 10.00;   //Guaranteed minimum hourly wage
   public static final int    WORK_WEEK_HOURS = 40;   //Expected maximum hours in a work week
   public static final int    WORK_DAY_HOURS  = 10;   //Expected maximum hours in a work day
   
   //Instance Variables
   private final String number;  //ID number
   private double payRate;       //Pay-rate
   
   //Constructor
   public Employee(double payRate)
   {
      this.number = newNumber();
      this.payRate = payRate;
   }
  
   //Accessor
   public String getNumber()
   {
      return this.number;
   }
   
   //Accessor
   public double getPayRate()
   {
      return this.payRate;
   }
   
   //For implementation in subclasses     
   public abstract double grossPay();
   
   //Override
   public String toString()
   {
      return this.getClass().getName() + " " + this.number + 
             "  Pay Rate $" + this.payRate ;
 
   }
   
   //Override 
   public boolean equals(Object other)
   {
      if (other == null || this.getClass() != other.getClass())
         return false;
      
      Employee that = (Employee)other;  
      return this.number.equals(that.number) &&
             this.payRate == that.payRate;
   }
       
   //Helper: Create unique Employee number in the form x-xxx-xxx
   private static int nextNumber = 7000000;
   private static String newNumber()
   {
      String number = "" + (++nextNumber);
      return number.substring(0, 1) + "-" +
             number.substring(1, 4) + "-" +
             number.substring(4);
   }
   
   //Overide to implement Comparable interface
   public int compareTo(Object other)
   {
      return this.number.compareTo(  ((Employee)other).number );
   }
}