Instance

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Instance methods
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Method
We found that it's more appropriate to put these
method inside the BankAccount class
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An ideal class

• The BankAccount class is ideally suited to
  contain/store
• Information about BankAccount ( instance
  variables)
• Operations on BankAccount variables ( method)
• Remember that program data algorithm

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New notation to invoke a method
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Terminology

• A class method
• Methods defined with the keyword static
• An instance method
• Methods defined without the keyword static

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Shadowing a instance variable (1)

• When the method has
• local/parameter variable 
  class/instance variable
• The class/instance variable can no
  longer accessible with the short
  hand notation in that scope

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This (1)
The Java compiler always assume that the type of
the variable this is
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This (2)

• A variable name used inside a method
• that matches the name of a local/parameter
  variable refers to the local/parameter variable
• Otherwise
• it refers to a class variable or an instance
  variable

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Shadowing a instance variable (2)

• Overcome the shadowing problem with instance
  variables
• Use the full name to access the instance
  variable

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Object-oriented programming (OOP)

• An object is an entity with some state
  information and a set of well-defined operations
• It can be used to represent something in the real
  world
• It can be used to organize information used
  inside a computer program.

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Implementing an object

• Represent the state information of the
  object accurately 
• with (instance) variables, 
• and
• Represent the operations on the
  object accurately 
• with (instance) methods

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Copying an object (1)

• Both an object and an array are accessed through
  a reference variable

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Copying an object (2)
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Copying an object (3)
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Copying an object (4)
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Classes with private variables (1)

• Security/correctness considerations in computer
  programming

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Classes with private variables (2)

• If there exist complex relationships between diffe
  rent 
• instance variables, we must maintain the relati
  onship correctly
• Granting unrestricted access to the instance
  variables can result in incorrect changes and can
  give result in data inconsistency

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Classes with private variables (3)

• public  there are no access restrictions to
  a variable or 
• method

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Classes with private variables (4)

• private  access is restricted to the same class

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Classes with private variables (5)