CIS283: Introduction to Application Programming with Java

1
CIS283 Introduction to Application Programming
with Java

• Jose perez-carballo
• Summer 2008
• Day 6

2

• Announcements
• Earlier today I sent scores on all previous
  assignments
• Please let me know if you think you submitted
  some assignment that I didnt count

3

• The Music DB project
• The Music database project is due next week (Aug
  21st)
• The specs are at http//www.calstatela.edu/facult
  y/jperezc/courses/CIS283/assignments/MusicDB/index
  .html
• You should write code that complies with the
  specs above

4

• The Music DB project
• Please download http//www.calstatela.edu/faculty/
  jperezc/courses/CIS283/assignments/MusicDB/Test.cl
  ass
• Into the same directory where you have all your
  MusicDB classes
• Add the following code to your Driver.java file
• Test tt new Test()
• tt.runTests()

5

• The Music DB project
• Compile your project
• javac java
• Run the program
• java Driver
• Two numbers are printed similar to following
• first code 9989336
• second code 29968085
• When you are done debugging please enter the two
  numbers in the web form that you will find in out
  website

6

• Packages, Interfaces, and Other Class Features

7

• Modifiers
• modify the declarations
• To define access public, protected and private
• To create class methods and variables static
• To finalize the implementations of classes,
  methods and variables final
• To create abstract classes and methods abstract
• To be used with threads synchronize and volatile

8

• The modifier precedes the declaration
• public class bycicle extends vehicle
• private boolean online
• static final double weeks 9.5
• protected static final int MEANIN_OF_LIFE 42
• public static void main(String args)

9

• The return type is not a modifier
• If there are several modifiers they can appear in
  any order (as lng as they precede everything
  else)
• public static void main(String args)

10

• Modifiers are optional
• If you dont use any modifier Java assumes some
  reasonable deafults

11

• Access modifiers
• public vs private
• Encapsulation

12

• Access modifiers
• The default is public
• Class Person
• String first
• private String last
• Class Driver
• Public static void main(String args)
• //test access modifiers of Persons fields

13

• Neither private variables or methods are
  inherited by subclasses
• All public methods and classes are inherited
• Test this

14

• Methods should be used to control access to
  private fields
• These methods enforce encapsulation
• In general it is considered to be good practice
  to make the class fields private and the methods
  used to control them public
• They are called accessor methods
• They may perform some tests
• Example setZicode(int) and getZipcode()

15

• A protected variable (or method) is inherited but
  not public

16

• The static modifier
• Used to create class variables and methods

17

• final modifier
• the final modifier is used with a variable to
  indicate its value will not change
• It is a constant
• The convention is to use only uppercase for such
  variables
• public static PI 3.1416

18

• packages
• Like a library,
• It is a collection of related classes
• Used to organized large quantities of classes

19

• ArrayList is in package java.util
• You can use it as follows
• java.util.ArrayListltStringgt db new
  java.util.ArrayListltStringgt()
• Or you can write
• import java.util.ArrayList
• At the beginning of your file and then
• ArrayListltStringgt db new ArrayListltStringgt()

20

• x
• x