Spring Semester 2005


Lecture Notes Nineteen: Practice Problems

Try to solve these problems to practice some of the things you learned this week. In the examples that follow, your program's answers are always in blue, to distinguish them from what you would type as a user. Remember: the resulting programs are elementary, and the problems are interesting.

For all of these problems the use of BlueJ is recommended.

1. Write a program that asks for an initial balance amount. Create a BankAccount object with that amount. Then ask for a deposit amount and a withdrawal amount. Carry out the deposit and withdrawal, then print the remaining balance. Use ConsoleReader from Lab Notes Two, and please place your main method in the class BankAccount.
Here's a sample run of such a program:
frilled.cs.indiana.edu%javac BankAccount.java
frilled.cs.indiana.edu%java BankAccount
Hello, and welcome to JavaOne Bank.
An account will be created for you.
What will the initial balance be?
Type it now: 
-40.2
The current balance in your account is: -40.2
You now want to make a deposit. How much?
Type the amount here: 
120.3
The current balance in your account is: 80.1
You now want to make a withdrawal. How much?
Type it now: 
34
The current balance in your account is: 46.099999999999994
Thanks for using class BankAccount. Good-bye!
frilled.cs.indiana.edu%


2. Implement a class Employee. An employee has a name (a String) and a salary (a double). Write a default constructor, a constructor with two parameters (name and salary), and methods to return the name and salary. Write a small program to test your class.
Here's a sample run of such a program:
frilled.cs.indiana.edu%java Employee
Creating a new employee.
Please type the name:
Larry Bird
Please specify the salary:
200000
New employee has been created.
Name of employee: Larry Bird
Salary: 200000.0
Thank you for testing class Employee.
frilled.cs.indiana.edu%

3. Implement a class Employee. An employee has a name (a String) and a salary (a double). Write a default constructor, a constructor with two parameters (name and salary), and methods to return the name and salary. Test your program, then enhance the class by adding a method
raiseSalary(double byPercent)
that raises the employee's salary by a certain percentage.
Here's a sample run of such a program:
frilled.cs.indiana.edu%java Employee
Creating a new employee.
Please type the name:
Michael Jordan
Please specify the salary:
300000
New employee has been created.
Name of employee: Michael Jordan
Salary: 300000.0
Raising the salary of Michael Jordan
By what percentage (e.g., 10, 20, etc.)?
10.5
Name of employee: Michael Jordan
Current salary: 331500.0
Thank you for testing class Employee.
frilled.cs.indiana.edu%

4. Implement a class Car with the following properties. A car has a certain fuel efficiency (measured in miles per gallon or liters per km -- pick one) and a certain amount of fuel in the gas tank. The efficiency is specified in the constructor,and the initial fuel level is 0. Supply a method drive that simulates driving the car for a certain distance, reducing the fuel level in the gas tank, and methods getFuelLevel, returning the current fuel level, and tank, to tank up.
Sample usage of the class:
public static void main(String[] args) {
  Car myBeemer = new Car(29);
  System.out.println(myBeemer.getFuelLevel()); 
  myBeemer.tank(20); 
  System.out.println(myBeemer.getFuelLevel()); 
  myBeemer.drive(100); 
  System.out.println(myBeemer.getFuelLevel()); 
} 
Should produce:
frilled.cs.indiana.edu%java Car
0.0
20.0
16.551724137931036

7. Implement a class Student. For the purpose of this exercise, a student has
  • a name and
  • a total quiz score
Supply an appropriate constructor and methods
  • getName()
  • addQuiz(int score)
  • getTotalScore(), and
  • getAverageScore()

To compute the latter, you also need to store the number of quizzes that the student took.

Here's a sample run of such a program:
public static void main(String[] args) {
    Student a = new Student("Larry"); 
    a.addQuiz(10);
    a.addQuiz(9); 
    a.addQuiz(8); 
    System.out.println("Grade report for: " + a.getName()); 
    System.out.println("Total score: " + a.getTotalScore()); 
    System.out.println("Average score: " + a.getAverageScore()); 
}
Should produce:
frilled.cs.indiana.edu%java Student
Grade report for: Larry
Total score: 27.0
Average score: 9.0
frilled.cs.indiana.edu%

8. Implement a class Product. A product has
  • a name and
  • a price
For example
new Product("Toaster", 29.95)
Supply methods
  • printProduct()
  • getPrice(), and
  • setPrice()
Write a program that
  • makes two products,
  • prints them,
  • reduces their prices by $5.00, and then
  • prints them again
Here's a sample run of such a program:
public static void main(String[] args) {
    Product a = new Product("Toaster", 29.95); 
    Product b = new Product("Phone", 35.55); 
    a.printProduct(); 
    a.setPrice(a.getPrice() - 5.00); 
    a.printProduct(); 
    b.printProduct(); 
    b.setPrice(b.getPrice() - 5.00); 
    b.printProduct(); 
} 
Should produce:
frilled.cs.indiana.edu%java Product
Product name: Toaster
Product price: 29.95
------------------------------
Product name: Toaster
Product price: 24.95
------------------------------
Product name: Phone
Product price: 35.55
------------------------------
Product name: Phone
Product price: 30.549999999999997
------------------------------
frilled.cs.indiana.edu%

9. Implement a class Circle that has methods
  • getArea() and
  • getCircumference()
In the constructor, supply the radius of the circle.
Here's a sample run of such a program:
public static void main(String[] args) {
    ConsoleReader c = new ConsoleReader(System.in); 
    System.out.println("Please specify the radius of your circle:"); 
    Circle a = new Circle(c.readDouble()); 
    System.out.println("Circle created. "); 
    System.out.println("Area: " + a.getArea()); 
    System.out.println("Circumference: " + a.getCircumference()); 
    System.out.println("Good-bye!"); 
}
Should produce:
frilled.cs.indiana.edu%java Circle
Please specify the radius of your circle:
1.0
Circle created. 
Area: 3.141592653589793
Circumference: 6.283185307179586
Good-bye!
frilled.cs.indiana.edu%java Circle
Please specify the radius of your circle:
3.14
Circle created. 
Area: 30.974846927333928
Circumference: 19.729201864543903
Good-bye!
frilled.cs.indiana.edu%

10. Implement a class BeerCan with methods
  • getSurfaceArea() and
  • getVolume()
In the constructor, supply the height and radius of the can.
Here's a sample run of such a program:
public static void main(String[] args) {
    ConsoleReader c = new ConsoleReader(System.in); 
    System.out.println("Please specify the height of the BeerCan."); 
    double height = c.readDouble(); 
    System.out.println("Please specify the radius of the BeerCan."); 
    double radius = c.readDouble(); 
    BeerCan b = new BeerCan(height, radius); 
    System.out.println("The BeerCan has been created."); 
    System.out.println("Its surface area is: " + b.getSurfaceArea()); 
    System.out.println("Its volume is: " + b.getVolume()); 
}
Could produce:
frilled.cs.indiana.edu%java BeerCan
Please specify the height of the BeerCan.
2.5
Please specify the radius of the BeerCan.
1.0
The BeerCan has been created.
Its surface area is: 15.707963267948966
Its volume is: 7.853981633974483
frilled.cs.indiana.edu%java BeerCan
Please specify the height of the BeerCan.
2
Please specify the radius of the BeerCan.
1
The BeerCan has been created.
Its surface area is: 12.566370614359172
Its volume is: 6.283185307179586
frilled.cs.indiana.edu%

Good luck and don't forget: the harder they seem the more you can learn from them.

But these problems are not difficult. They're just that: good practice.


Last updated: March 22, 2005 by Adrian German for A201