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Final Exam Review

Note: This focuses more on the latest material; please also review the material for the midterm.

  1. Write a class called Fraction with the following methods/constructor:

    • A constructor that takes two int parameters, the numerator and denominator, respectively
    • a method called getNumerator, that returns an int, the numerator
    • a method called getDenominator, that returns an int, the denominator
    • a method called toDouble, that returns a double, the equivalent decimal to the fraction.

  2. Given the following interface:

interface Product {
    public String getName();
    public String getType();
    public double getPrice();
}

Create a class Book that implements the Product interface; it should return "Book" for getType(), and have a constructor taking the other two fields.

  1. Write a Java code fragment to create a variable called b1, of type Book (defined above) and assign it to a Book instance with name "Catch 22" and price 7.95

  2. Given the Product interface above, write a function called AveragePrice, that takes an array of Product, and returns a double, the average price of the product.

  3. Given the Product interface above, write a function called HighestPricedProduct, that takes a List of Product, and returns a Product, the product with the highest price.

  4. Java has an Integer class, with a static method parseInt, that takes a string and returns an int. This function throws a NumberFormatException if the string does not represent a valid int. Write a static function called parseInt, which takes two arguments, a String and an int (the int represents the default value), and returns an int. This function calls Integer.parseInt, and handles the exception so that, if parseInt raises a NumberFormatException the function would return the default value.

  5. Given the Fraction class you created above, write a static createFraction method, that takes two integers, the numerator and denominator, and returns a Fraction with that numerator and denominator; however, if the denominator is zero, the function will throw an IllegalArgumentException (this class is defined by java and has a constructor with no arguments and one which takes a String argument for an error message, if you prefer).

  6. Write a function called ArrayFrequencies, that takes a List of Strings, and returns a Map of String to Int. The function maps every String in the array to its frequency (so if the string appears 3 times, it would be in the map paired with a value of 3). Hint- HashMap is the standard class for Maps. Map has methods containsKey, put and get.

  7. Write a function called MostCommonWord, that takes a List of Strings and returns the String which occurs more frequently in the list. You can assume the array contains no null values. Hint-Can call function above. Map also has methods keySet and entrySet which may be useful. EntrySet returns a Collection of Map.Entry ; Map.Entry has getKey() and getValue().