CIS283: Introduction to Application Programming with Java

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CIS283 Introduction to Application Programming
with Java

• Jose perez-carballo

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• The ABCs of programming

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• Statements and expressions
• A statement does something
• int A
• A 3

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• An expression is a statement (or part of a
  statement) that produces a value
• 2 3
• 2 gt 3
• concatenate this

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• A block of statements is delimited by
• and

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• Look for
• statemements
• Expressions
• And blocks
• In http//www.calstatela.edu/faculty/jperezc/cours
  es/CIS283/examples/chapter1/VolcanoApplication.jav
  a
• And
• http//www.calstatela.edu/faculty/jperezc/courses/
  CIS283/examples/chapter1/VolcanoRobot.java

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• Variables
• Place to store values
• A variable has
• Name
• type

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• Before a variable can be used it must be declared
• int a

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• Values can be assigned to variables
• A 3

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• The value of an expression can be stored in a
  variable
• A 3 4/2

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• The value stored in a variable can be changed
  while the program is running
• A 3
• A 5

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• A variable can be given an initial value
  (initialized) when it is declared
• int A 3

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• Look for
• variables
• Declarations
• Initial values in
• http//www.calstatela.edu/faculty/jperezc/courses/
  CIS283/examples/chapter1/VolcanoApplication.java
• And
• http//www.calstatela.edu/faculty/jperezc/courses/
  CIS283/examples/chapter1/VolcanoRobot.java

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• Instance variables store object attributes
• Examples?
• Class variables store for all objects of a class
• Examples?
• Local variables exist only inside a block, when
  the block is finished executing its local
  variables are destroyed

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• Look for instance, class and local variables in
• http//www.calstatela.edu/faculty/jperezc/courses
  /CIS283/examples/chapter1/VolcanoApplication.java
• And
• http//www.calstatela.edu/faculty/jperezc/courses/
  CIS283/examples/chapter1/VolcanoRobot.java

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• If not given an initial value Java intializes
• Numeric variables to 0
• characters to \0
• Booleans to false
• Objects to null

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• Naming variables
• A variable can be
• Any sequence of numbers, letters (upper/lower
  case), _, and
• They cannot start with a number
• Java uses Unicode characters

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• Which are valid variables
• 1JavaVariable
• One_Java
• javac
• _javac
• JavaVariable
• JavaVariable
• java123Variable
• café

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• Conventions
• thisIsAGoodName
• thisisnotsogood

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• Variable types
• One of the eight primitive types
• A class or an interface
• An array

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• Primitive types
• Integers (positive and negative)
• byte 8 bits
• short 16
• int 32
• long 64. E.g. 111111L
• Non integer numbers (positive and negative)
• double e.g. 2.2E2d
• float e.g 3.3E3f
• Characters
• char e.g. a
• Booleans
• boolean true or false

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• A class can be used as a type
• VolcanoRobot dante new VolcanoRobot()

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• If Animal is superclass of Elephant then
• Elephant clyde
• Animal aa
• aa clyde

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• Assignment statements
• Variable expression
• A 3 4

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• Constants
• final float PI 3.1416

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• Comments
• // this is a comment
• / this is a comment /
• / this is a comment /

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• Literals represent values directly
• 2008
• 2d
• 3f
• 0xFF
• 010
• 12e22

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• Java character escape codes
• \n New line
• \t Tab
• \b Backspace
• \r Carriage return
• \f Formfeed
• \\ Backslash
• \' Single quotation mark
• \" Double quotation mark
• \d Octal
• \xd Hexadecimal
• \ud Unicode character

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• String literals
• Real objects
• String Hello World!

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• Expressions
• x 3
• y x
• int z x 3

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• Artihmetic operators
• -
• /

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• Assignment operators
• -
• /

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• Incrementing and decrementing
• x
• x

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• Comparison operators
• !
• lt
• gt
• lt
• gt

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• Logical operators
• (shortcircuiting)
• (XOR)
• !

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• Operator precedence
• X 6 4 / 2
• (see table 2.6)

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• String concatenation
• append number 7 here

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• Downloading and installing Java
• https//jdk6.dev.java.net/ download Windows
  Offline Installation, Multi-language JDK file
• See installation instructions http//java.sun.com
  /javase/6/webnotes/install/index.html
• See also Appendix A