Java Syntax, Java Conventions, CSE 115 Conventions (Part 2)

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Java Syntax, Java Conventions, CSE 115
Conventions (Part 2)

• CSE 115
• Spring 2006
• January 30, February 1 3, 2006

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VII - Constructors

• Q What is the job of the constructor?
• Identifying the constructor in code
• public class SomeName
• public SomeName()
• Between the is the Java code that outlines
  what the functionality of the constructor is.

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VII Constructors continued

• When we actually want to create an object, we
  need to activate the capability of the
  constructor, we do so by inserting the following
  line of code into our program
• new NameOfConstructor()

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VIII - Keywords

• Sometimes called reserved words, these words have
  a special meaning in Java and can only be used
  for that purpose within your code.
• Please note the listing of keywords for this
  semester linked off of the Resources page

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IX - Identifiers

• Programmer defined names for program elements
  (names)
• Rules
• Begin with a letter or underscore
• Followed by zero or more letters, numbers,
  underscores
• No spaces or special characters allowed in
  identifiers
• Keywords are not allowed to be identifiers

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XI - Dependency

• Relationship between two classes
• Informally called uses a
• Represented in UML diagrams as a dotted arrow
• In code, if ClassA uses a ClassB
• public class ClassA
• public ClassA()
• new ClassB()

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XII - Packages

• package keyword indicates the class membership
  in a package.
• Packages are ways to organize code so that code
  with like purpose is kept together.

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XIII - Comments

• Notes to help us remember/understand the code we
  write
• Two styles
• // to the end of line comment
• / Multi-line comment begin
• Multi-line comment ends with /

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XIV - Composition

• Second relationship between classes
• Informally called has a
• Represented in UML with a diamond-headed arc
• In code
• Declare an instance variable
• Create an instance of the component part
• Assign that instance to the instance variable

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XV - Variables

• Named storage

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XVI Instance Variables

• Variables that store information specific to a
  class used to store all three types of
  properties discussed earlier.
• Declaring an instance variable
• visibility type identifier

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XVII Visibility

• Access control modifiers indicate who has access
  to something
• Visibilities are presented by keywords
• private
• public
• Q What is the difference between the two types
  of visibilities?

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XVIII Type of a variable

• Java is strongly-typed
• When variables are declared, we must tell Java
  what type of thing the variable will hold on to

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XIX Identifiers for instance variables

• Begin with an underscore
• First letter of first word lower case
• First letter of subsequent words upper case
• _myFirstInstanceVariable