// Fig. 9.4: CommissionEmployee.java
// CommissionEmployee class represents an employee paid a 
// percentage of gross sales.
public class CommissionEmployee extends Object {
   private final String firstName;                        
   private final String lastName;                         
   private final String socialSecurityNumber;             
   private double grossSales; // gross weekly sales       
   private double commissionRate; // commission percentage

   // five-argument constructor                                
   public CommissionEmployee(String firstName, String lastName,
      String socialSecurityNumber, double grossSales, 
      double commissionRate) {
      // implicit call to Object's default constructor occurs here   

      // if grossSales is invalid throw exception
      if (grossSales < 0.0) {
         throw new IllegalArgumentException("Gross sales must be >= 0.0");
      }   

      // if commissionRate is invalid throw exception
      if (commissionRate <= 0.0 || commissionRate >= 1.0) {
         throw new IllegalArgumentException(
            "Commission rate must be > 0.0 and < 1.0");
      }   

      this.firstName = firstName;                                    
      this.lastName = lastName;                                    
      this.socialSecurityNumber = socialSecurityNumber;         
      this.grossSales = grossSales;
      this.commissionRate = commissionRate;
   } 

   // return first name
   public String getFirstName() {return firstName;}

   // return last name
   public String getLastName() {return lastName;}

   // return social security number
   public String getSocialSecurityNumber() {return socialSecurityNumber;}

   // set gross sales amount
   public void setGrossSales(double grossSales) {
      if (grossSales < 0.0) {
         throw new IllegalArgumentException("Gross sales must be >= 0.0");
      }

      this.grossSales = grossSales;
   } 

   // return gross sales amount
   public double getGrossSales() {return grossSales;}

   // set commission rate
   public void setCommissionRate(double commissionRate) {
      if (commissionRate <= 0.0 || commissionRate >= 1.0) {
         throw new IllegalArgumentException(
            "Commission rate must be > 0.0 and < 1.0");
      }

      this.commissionRate = commissionRate;
   } 

   // return commission rate
   public double getCommissionRate() {return commissionRate;}

   // calculate earnings                                         
   public double earnings() {return commissionRate * grossSales;}

   // return String representation of CommissionEmployee object         
   @Override // indicates that this method overrides a superclass method
   public String toString() {                                           
      return String.format("%s: %s %s%n%s: %s%n%s: %.2f%n%s: %.2f",     
         "commission employee", firstName, lastName,                    
         "social security number", socialSecurityNumber,                
         "gross sales", grossSales,                                     
         "commission rate", commissionRate);                            
   }                                                                    
} 


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