Session 6
Module 8: More on Classes
Module 9: Exceptions
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Module 7 - Review

Inheritance

Overloading of methods

Using abstract keyword

Using final keywords

Interfaces
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Module 8 - Objectives

Class variables

Nested class
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Class variables

Are declared using the static keyword

Once the value is modified, all instances of the class are
updated to share the same value
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Access Class variables


keyword

It initializes the static
variables in class

The static initialization block
can reference only class
variables that have been
declared before it
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Nested class

A class defined within another class

It can have access to members of the outer class
(enclosing class) even if the members are declared
private

It can be used for:

Allow logical grouping of classes

Increases encapsulation

More maintainable code
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Different type of nested class

Member classes or non-static nested classes



A static nested class is
associated with its outer class.

It cannot refer directly to
instance variables or methods
defined in its enclosing class,
but it can access class
methods or variables directly.

An object needs to be
instantiated to access the
instance variables and
methods of the enclosing
class.
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Module 9 - Objectives

Introduction to Exceptions

Exception handling in Java

User defined exceptions

Assertions
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Introduction to Exceptions

Explain the concept of Exceptions



Raised by runtime environment, such as memory error or network
connection failure error.

These exceptions that are not expected to be caught by the client
code
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Classification of Exceptions

Checked Exceptions

Unchecked
Exceptions
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Checked Exceptions

Generated in situations that occur during the normal
execution of a program. For example:

Requesting for missing file, invalid user input, and network
failures.

These exceptions should be handled to avoid
compile-time errors. It is checked during the
compilation.
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Types of Checked Exceptions
All Checked exceptions are derived from the Exception class.
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Unchecked Exceptions


Describe the use of multiple catch block
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The use of try-catch block
try {
Statement_1;
Statement_2;
…
}
catch(ExceptionType ObjectName){
Statement_1;
}
Syntax