Classes:%20user-defined%20types

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Classes user-defined types
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Organizing method with a class

• A class is used to organize methods
• Methods that compute Mathematical functions 
• The Scanner class

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Organizing information with a class

• A class can also be used to organize information
• It defines a group of related information that
  belong to the same entity

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Instance Variables (1)

• Java has 4 different kinds of variables
• 1. Local variables
• 2. Parameter variables

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Instance Variables (2)
3. Class variables
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Instance Variables (3)

• 4. Instance variables 
• are defined inside some class
• are defined outside every method of that class.
• are defined without using the keyword static

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Creating an object in Java (1)

• Define a variable to store the location of
  the object.
• Create the object

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Creating an object in Java (1)
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Creating an object in Java (2)
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Accessing the information stored inside an object
(1)
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Accessing the information stored inside an object
(2)
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Accessibility rule for instance variables

• The accessibility of instance variables are
  controlled by access modifiers 
• public   can be accessed in a method
  inside any class
• private  can be accessed  in a method
  inside the same class

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Lifetime of Instance variables (1)
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Lifetime of Instance variables (2)
These instance variables will cease to
exist after the garbage collection
procedure has completed execution
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Methods using a object variable as parameter (1)

• A class in Java is equivalent to a data type

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Methods using a object variable as parameter (2)

• Variable x and variable stu1 will access
  the same memory locations

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Changing the values of a variable inside an object