public class Apartment {
    private int bedrooms;
    private double rent;

    public Apartment(int rooms, double amount) {
        if (rooms < 0) 
			rooms = 0;    // check for valid value
        if (amount < 0) 
			amount = 0;  // check for valid value
        bedrooms = rooms;
        rent = amount;
    }

    public int getNumberofBedrooms() { return bedrooms; }       

    public double getRent() { return rent; }

    public void raiseRent(double amount) {
        // we'll allow a negative amount, i.e. rent is lowered
        rent += amount;
    }

    public boolean isEfficiency() {
        return bedrooms == 0;
    }

    public boolean isExpensive() {
        return rent > 500 + 150 * bedrooms;
    }
}