/**
 * TractorTrailer.java
 *
 * A class that represents a tractor trailer.  It is a subclass of Truck.
 *
 * It inherits fields and methods from Truck and Vehicle.
 *
 * Computer Science 112
 */

public class TractorTrailer extends Truck {
    private boolean isSleeper;    // does this tractor trailer have a sleeping compartment?

    /**
     * constructor that takes the make, model, year, and number of wheels
     */
    public TractorTrailer(String make, String model, int year, int numWheels) {
        // Invoke the Truck constructor to initialize
        // the fields inherited from Truck and Vehicle.
        super(make, model, year, numWheels);
       
        
        // default value, which can be changed using setIsSleeper()
        this.isSleeper = false;
    }
    
    /*** accessors ***/
    // getMake(), getModel(), etc. are inherited from Vehicle.
    // getCapacity() and getNumAxles() are inherited from Truck.

    public boolean isSleeper() {
        return this.isSleeper;
    }

    /**
     * TractorTrailer version of getNumAxles().
     * We override the version inherited from the Truck class.
     * That version doesn't work for tractor trailers, because they
     * have four wheels on most of their axles.
     */
    public int getNumAxles() {
        // number of wheels on all but the front axle
        int numBackWheels = this.getNumWheels() - 2;  
        return 1 + numBackWheels/4;
    }
    
    /*** mutators ***/
    /** setMileage and setPlateNumber are inherited from Vehicle. **/
    /** setCapacity() is inherited from Truck. **/
    
    public void setIsSleeper(boolean isSleeper) {
        this.isSleeper = isSleeper;
    }
}