CSE110 Lecture 19

Principles of Programming with Java
constructors, getters and setters
(202006)

Transcript

1. CSE110
   Principles of Programming
   with Java
   Lecture 19:
   Methods: constructor, getter, and setter
   Javier Gonzalez-Sanchez
   javiergs@asu.edu
   javiergs.engineering.asu.edu | javiergs.com
   Office Hours: By appointment
   

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2. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 4
   Methods
   class
   

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3. Constructors
   

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4. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 6
   Constructor Method
   • A constructor is a special method that is used to create
   a new object.
   • Each class has a default constructor (without parameter)
   even if a programmer does not define one.
   • Each constructor has the following properties:
   • it has the same name as the class
   it does not have any return type, not even void
   • it is always called/used with the reserved word
   “new”.
   • it typically sets the initial values of instance variables
   • We can create multiple constructor methods for one
   class.
   

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5. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 7
   Example
   

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6. Getters and Setters
   

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7. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 9
   Getters and Setters
   • Encapsulation is one of the four fundamental OOP
   concepts.
   • In encapsulation, the variables of a class will be
   hidden from other classes and can be accessed
   only through the methods of their current
   class. Therefore, it is also known as data hiding.
   • To achieve encapsulation in Java:
   • Declare the variables of a class as private.
   • Provide public setter and getter methods to
   modify and view the variables values.
   

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8. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 10
   Example
   

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9. CSE110 - Principles of Programming
   Javier Gonzalez-Sanchez
   javiergs@asu.edu
   Summer 2020
   Disclaimer. These slides can only be used as study material for the class CSE110 at ASU. They cannot be distributed or used for another purpose.
   

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