I want the class, BasePlusCommissionEmployee, to contain a reference to a CommisionEmployee object. Instead of the inheritance.   *Code in Question below* public class CommissionEmployee {         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 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 getCommissionRate() * getGrossSales();    }             // return String representation of CommissionEmployee object         @Override         public String toString() {            return String.format("%s: %s %s%n%s: %s%n%s: %.2f%n%s: %.2f",               "commission employee", getFirstName(),getLastName(),               "social security number", getSocialSecurityNumber(),               "gross sales",getGrossSales() ,               "commission rate", getCommissionRate() );         }     }       --------------------------------------------------------------------------------------------------------------------------------------------------    public class BasePlusCommissionEmployee extends CommissionEmployee {        private double baseSalary; // base salary per week        // six-argument constructor    public BasePlusCommissionEmployee(String firstName, String lastName,        String socialSecurityNumber, double grossSales,        double commissionRate, double baseSalary) {        super(firstName, lastName, socialSecurityNumber,           grossSales, commissionRate);                              // if baseSalary is invalid throw exception        if (baseSalary < 0.0) {                            throw new IllegalArgumentException("Base salary must be >= 0.0");        }            this.baseSalary = baseSalary;     }     // set base salary     public void setBaseSalary(double baseSalary) {        if (baseSalary < 0.0) {                             throw new IllegalArgumentException("Base salary must be >= 0.0");        }            this.baseSalary = baseSalary;                     }     // return base salary     public double getBaseSalary() {return baseSalary;}     // calculate earnings     @Override     public double earnings() { }     // return String representation of BasePlusCommissionEmployee40    @Override     public String toString() {     } }