1. Set & Get Methods ICS 111: Introduction to Computer Science I
William Albritton
Information and Computer Sciences Department at the University of Hawai‘i at Mānoa
"There is no reason anyone would want a computer in their home."
Ken Olson, president, chairman and founder of Digital Equipment Corp., 1977
11/20/2018
© 2007 William Albritton

2. Last Assignment Go over last assignment
General steps for writing a class definition
Class name at top
Write the data fields
Write the constructor
Write the methods
General steps for writing main() method of client program, which uses class definition
Instantiate (create) an object of the class definition
Call the methods of the class definition
Display the results of the methods
11/20/2018
© 2007 William Albritton

3. Accessor Methods Simple methods that get a data field
Usually start with “get”
Have return values but no parameters
Used to return data to the calling method
Name name = new Name("Nami","Suzuki"); String firstName = name.getFirst(); //firstName is "Nami"
public String getFirst(){ return first; }
11/20/2018
© 2007 William Albritton

4. Mutator Methods Simple methods that set a data field
Usually start with “set”
Have parameters but no return value
Used to change the value of a data field
Name name = new Name("Nami","Suzuki"); name.setFirst("Nancy"); String herName = name.toString(); //herName is "Nancy Suzuki"
public void setFirst(String firstP){ first = firstP; }
11/20/2018
© 2007 William Albritton

5. Class Name
Class Name has several methods that are typical methods of other classes
Constructor to initialize data fields of object
toString() method to output the data fields
Access (get) method to access each data field individually
Mutator (set) method to change each data field individually
See Name.java & NameClient.java
11/20/2018
© 2007 William Albritton

6. Class Exercise 1
Write class Point & a client program that uses objects of class Point
The Point class definition should have
Two integer data fields (for x & y)
A constructor
A toString() method
A mutator (set) & accessor (get) method for both x & y (so 4 methods)
The client program’s main() method should
Instantiate (create) an object of class Point
Call the methods of class Point
Output the results of the methods
11/20/2018
© 2007 William Albritton

7. Class Fraction
Class Fraction has several methods that are typical methods of other classes
Constructor to initialize data fields of object
toString() method to output the data fields
Access (get) method to access each data field individually
Mutator (set) method to change each data field individually
See Fraction.java & FractionClient.java
11/20/2018
© 2007 William Albritton

8. Constructor & Parameters
Your formal & actual parameters have to have the same type, and the same number of parameters
For example, these statements do not compile
Fraction fraction1 = new Fraction("5", "3");
Fraction fraction2 = new Fraction(12.3, 3.98);
Fraction fraction3 = new Fraction(5, 6, 7);
11/20/2018
© 2007 William Albritton

9. Class Exercise 2
List all the variables in Exercise2.java (class Car & client program)
For each variable, write the following:
The kind of variable (data field, parameter, or local variable)
The scope (specific line numbers)
11/20/2018
© 2007 William Albritton

10. Class Kurochan
Class Kurochan has several methods that are typical methods of other classes Constructor to initialize data fields of object
draw() method to display the drawing
Access (get) method to access each data field individually
Mutator (set) method to change each data field individually
See Kurochan.java & KurochanClientApplet.java & kurochan.html
The client program uses get() & set() to draw several Kurochans diagonally
11/20/2018
© 2007 William Albritton

11. Class Exercise 3 What is the output of the following program?
Exercise3.java
11/20/2018
© 2007 William Albritton