Basic To Advanced Selenium Java Full Course - Session 4 - Handling Exceptions, Collections Framework

Handling Exceptions:

An exception is an unexpected event that disrupts the normal flow of program

Types of Java Exception:

Checked Exception - These exceptions are checked at compile time. Ex: IOException, SQLException

Unchecked Exception - These exceptions are checked at run time. Ex: ArithmeticException, Null Pointer Exception, ArrayIndexOutOfBoundsException

Exception Handling can be performed by using the below keywords:

try - Code which is expected to return exceptions can be placed inside try block

catch - It contains the code which is used to handle the exception

finally - Code which must execute whether or not exception occurs is kept in finally block

throw - It is used to throw an exception

throws - If a method throws an exception it must be declared by using throws keyword

Collections:

Collection is an object which represents a group of objects

Collections framework is a unified architecture for representing and manipulating collections

Collections can be used to perform all operations on data like sorting, insertion, manipulation and deletion

Reduces programming efforts by providing in built algorithms and data structures

Increases performance by providing high performance implementations of data structures and algorithms

Increases code reuse by providing standard interface for collections and algorithms

Array List:

ArrayList is a dynamic array for storing elements

Elements can be added and removed easily from a array list

It can contain duplicate elements

It maintains the insertion order of the elements

Methods:

add() To insert specific element in specific position

clear() To remove all elements from the list

get() To fetch element from particular position in the list

set() To change the element in the list

remove() To remove the first occurrence of specified element

size() To return the elements present in the list

indexOf() To get index of first occurrence of an element in the list

HashMap:

It stores the data in key value pairs where keys should be unique

It can contain one null key but multiple null values

It doesn’t maintain order of elements

It is non synchronized i.e. multiple threads can access it simultaneously

It uses a technique called Hashing which converts a large string to small string that represents the same string. A shorter value helps in indexing and faster searches

HashMap Methods:

get() Returns the value associated with specified key

put() Used to insert an entry in the map

isEmpty() Returns true if map contains no key value mappings

Remove() Used to delete an entry for the specified key

containsKey() Returns true if the specified key exists in the map

containsValue() Returns true if the specified value exists in the map

equals() Used to compare an object with map

clear() Used to remove all mappings from the map

entrySet() Returns a Set view of mappings contained in the map

keyset() Returns a Set view of the keys contained in the map

HashSet:

It implements the Set interface

Uses Hash Table to store data

Duplicate values are not allowed

Insertion order is not maintained

Null values are allowed

It is non synchronized

HashSet Methods:

add() Used to add the specified element to the set if it is not already present

clear() Used to remove all elements from the set

contains() Returns true if set contains the specified element

size() Returns the number of elements in the set

isEmpty() Returns true if the set contains no elements