public class Reading
{
    /** Returns the day number of this reading */
    public int getDay()
    { /* implementation not shown */ }

    /** Returns the temperature of this reading */
    public double getTemp()
    { /* implementation not shown */ }

    // There may be instance variables, constructors,
    // and methods that are not shown.
}

public class TempLog
{
    /** Readings in increasing day order; size() >= 1 */
    private ArrayList<Reading> readings;

    /** Returns a list of the day numbers on which the temperature
     *  rose by more than minRise compared with the previous reading.
     */
    public ArrayList<Integer> bigRises(double minRise)
    { /* to be implemented */ }

    // There may be instance variables, constructors,
    // and methods that are not shown.
}