public class Heater
{
    // instance variables - replace the example below with your own
    private double temperature;
    public Heater()
    {
        // initialise instance variables
        temperature = 15;
    }
    public void warmer()
    {
        // put your code here
        temperature = temperature + 5;
    }
    public void cooler()
    {
        // put your code here
        temperature = temperature - 5;
    }
}