Home > Articles

  • Print
  • + Share This
This chapter is from the book

Exercises

  1. Improve the Counter class in Section 5.1, “Simple Classes and Parameterless Methods,” on page 55 so that it doesn’t turn negative at Int.MaxValue.

  2. Write a class BankAccount with methods deposit and withdraw, and a read-only property balance.

  3. Write a class Time with read-only properties hours and minutes and a method before(other: Time): Boolean that checks whether this time comes before the other. A Time object should be constructed as new Time(hrs, min), where hrs is in military time format (between 0 and 23).

  4. Reimplement the Time class from the preceding exercise so that the internal representation is the number of minutes since midnight (between 0 and 24 × 60 – 1). Do not change the public interface. That is, client code should be unaffected by your change.

  5. Make a class Student with read-write JavaBeans properties name (of type String) and id (of type Long). What methods are generated? (Use javap to check.) Can you call the JavaBeans getters and setters in Scala? Should you?

  6. In the Person class of Section 5.1, “Simple Classes and Parameterless Methods,” on page 55, provide a primary constructor that turns negative ages to 0.

  7. Write a class Person with a primary constructor that accepts a string containing a first name, a space, and a last name, such as new Person("Fred Smith"). Supply read-only properties firstName and lastName. Should the primary constructor parameter be a var, a val, or a plain parameter? Why?

  8. Make a class Car with read-only properties for manufacturer, model name, and model year, and a read-write property for the license plate. Supply four constructors. All require the manufacturer and model name. Optionally, model year and license plate can also be specified in the constructor. If not, the model year is set to -1 and the license plate to the empty string. Which constructor are you choosing as the primary constructor? Why?

  9. Reimplement the class of the preceding exercise in Java, C#, or C++ (your choice). How much shorter is the Scala class?

  10. Consider the class

    class Employee(val name: String, var salary: Double) {
      def this() { this("John Q. Public", 0.0) }
    }

    Rewrite it to use explicit fields and a default primary constructor. Which form do you prefer? Why?

  • + Share This
  • 🔖 Save To Your Account