Reading:

1

• Reading
• 5.7, 6.1, 6.4, 7.3. 5

2
Type Conversion

• Implicit Type Conversion
• Means it happens even you dont ask for it.
• int j 34
• double d
• d j / 2.0
• Void fun (double x)
• fun (j)
• Explicit Type Conversion
• Means it happens if you ask for it.
• d double(j)/2

3
Type Conversion

• If a class has a constructor with only one
  parameter that constructor will be used by the
  compiler for implicit type conversion .
• For example
• StringOne x CDC

4
Different Programming Approaches

• Procedural
• Object Based
• Object Oriented

5
Class Relationships

• Association
• Composition
• Inheritance

6
Composition

• Composition represents a has-a relationship
  between two classes. In other word composition is
  implemented by making one class a member of the
  other class

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Composition (Continued)

• Composition denotes a whole/part relationship,
  with the ability to navigate from whole
  (aggregate) to its parts (attributes).
• The composition may or may not denote physical
  containment.
• Example The relationship between a shareholder
  and his shares is not physical containment.

8
Class Hierarchy

• Classes are related by inheritance
• A subclass inherits behavior and structure from
  its super-class.
• A subclass also augments or redefines the
  behavior and structure of its super-class.
• Also known as generalization/specialization
  hierarchy.

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Class Hierarchy (continued)

• Single inheritance
• Where subclasses can have only one immediate
  super-class.
• E.g.

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Inheritance

• Inheritance is a relationship among classes where
  a subclass inherits the structure and behavior of
  its super-class.
• Defines the is a or generalization/specializatio
  n hierarchy.
• Structure instance variables.
• Behavior instance methods.

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Inheritance (continued)

• A subclass may augment the existing structure and
  behavior of its super-class.
• A subclass may constrain or restrict the behavior
  inherited from its super-class.
• Single inheritance any class has at most one
  super-class.
• Multiple Inheritance where a subclass may have
  more than one super-class.

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Class derivation

• In order to derive a class, the following two
  extensions to the class syntax are necessary
• class head is modified to allow a derivation list
  of classes from which to inherit members
• class Window public Screen
• An additional class level, that of protected, is
  provided. A protected class member behaves as a
  public member to a derived class

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Class derivation (Continued)

• A super-classs instance variables are directly
  accessible to the subclass if they are declared
  protected.
• If declared private, these variables can only be
  accessed by sending messages to super (by
  invoking a super classs member function).

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Class derivation - Example
class Student public Person public
Student() protected char id

• class Person
• public
• Person()
• protected
• int age
• char name