In this post, I'm sharing the code snippet for Coding with Confidence: The Fun Way to Learn Salesforce Apex tutorial series part 8 and above below:

// * Collections in Apex

/*
*   There are 3 types of collections in apex:
*   1. List
*   2. Set
*   3. Map
*/

// * List - Part 1

// * List: A list is an ordered collection of elements. We can create a list of any data type like: primitive data types, collections, sObjects, custom data types etc.

// * Creating a list of names
List<String> names = new List<String>();
names.add('Richard Hendricks');
names.add('Monica');
names.add('Erlich Bachman');
names.add('Dinesh');
names.add('Gilfoyle');

System.debug('Names = ' + names);

// * Retrieving an element from the list
System.debug('Element at index 2 = ' + names[2]);

// * Replacing a list element at a particular index
names.set(2, 'Gavin Belson');
System.debug('Updated Names = ' + names);

names[2] = 'Erlich Bachman';
System.debug('Updated Names = ' + names);

// * Setting an index that doesn't exist
// names.set(10, 'Jared Dunn');

// names[10] = 'Jared Dunn';

// * Displaying the size of the list
System.debug('Size of list "names" = ' + names.size());

// * Clearing the list
names.clear();

System.debug('Size of list "names" = ' + names.size());
System.debug('Updated Names = ' + names);

// * List - Part 2

// * Checking if the list is empty
List<Integer> numbers = new List<Integer>();
System.debug('Numbers List = ' + numbers);
System.debug('Numbers List is empty = ' + numbers.isEmpty());

numbers.add(1);
numbers.add(2);

System.debug('Numbers List = ' + numbers);
System.debug('Numbers List is empty = ' + numbers.isEmpty());

// * Defining lists using array notation
String[] names = new String[5];
// List<String> names = new String[5];
// String[] names = new List<String>();
names[2] = 'Gavin Belson';
names[4] = 'Jared Dunn';
names[0] = 'Richard Hendricks';
names[1] = 'Erlich Bachman';
names[3] = 'Monica';
// names.add('Gavin Belson');
System.debug('Names Array = ' + names);
System.debug('Size of list "names" = ' + names.size());

// names[5] = 'Dinesh Chugtai';

names.add('Dinesh Chugtai');

System.debug('Updated Names = ' + names);
System.debug('Size of list "names" = ' + names.size());

// * Populating values inside a list at the time of initialization
List<String> names = new List<String>{'SFDC Stop', 'Rahul Malhotra'};
System.debug('Initial Names = ' + names);

String[] names = new String[]{'SFDC Stop', 'Rahul Malhotra'};
System.debug('Initial Names = ' + names);

// * List - Part 3

// * Sorting a list
List<String> names = new List<String>{'Richard Hendricks', 'Erlich Bachman', 'Gavin Belson', 'Monica', 'Jared Dunn', ''};
System.debug('Names = ' + names);
names.sort();
System.debug('Names in ascending order = ' + names);

// * Creating a list of collections
List<List<String>> names = new List<List<String>>(); // * Upto 8 levels
names.add(new List<String>{'Aman', 'Ashish', 'Adam', 'Anika'});
names.add(new List<String>{'Bob', 'Bhanu', 'Blake', 'Benjamin'});
System.debug('Names = ' + names);
System.debug('Names starting with "A" = ' + names[0]);
System.debug('Names starting with "B" = ' + names[1]);
System.debug('2nd name starting with "A" = ' + names[0][1]);
System.debug('3rd name starting with "B" = ' + names[1][2]);

// * Set

// * Set: A set is an unordered collection of elements that do not contain any duplicates. We can create a set of any data type like: primitive data types, collections, sObjects, custom data types etc.

// * Creating a set of integers
Set<Integer> numbers = new Set<Integer>();
numbers.add(2);
numbers.add(1);
numbers.add(4);
numbers.add(5);
numbers.add(3);

System.debug('Numbers Set = ' + numbers);
System.debug('Number of elements in Set = ' + numbers.size());

// * Adding duplicate elements inside set
numbers.add(1);
numbers.add(5);

System.debug('Numbers Set after adding duplicate elements = ' + numbers);
System.debug('Number of elements in Set = ' + numbers.size());

// * Check if 3 is present in set
System.debug('Is 3 present inside set = ' + numbers.contains(3));

// * Removing 3 from set
System.debug('Removing 3 from set...');
numbers.remove(3);

// * Check if 3 is present in set
System.debug('Is 3 present inside set = ' + numbers.contains(3));

System.debug('Numbers Set after removing 3 = ' + numbers);
System.debug('Number of elements in Set = ' + numbers.size());

// * Populating values inside a set at the time of initialization
Set<String> fruits = new Set<String>{'Mango', 'Apple', 'Banana', 'Pear', 'Mango'};
System.debug('Elements inside set of fruits = ' + fruits);

// * Map - Part 1

// * Map: A map is a collection of key-value pairs where each unique key maps to a single value. Keys and Values inside a map can be of any data type like: primitive data types, collections, sObjects, custom data types etc.

// * Creating a map of Integer, String:

Map<Integer, String> studentsMap = new Map<Integer, String>();
studentsMap.put(3, 'Gilfoyle');
studentsMap.put(5, 'Monica');
studentsMap.put(1, 'Richard Hendricks');
studentsMap.put(2, 'Dinesh');
studentsMap.put(4, 'Erlich Bachman');
studentsMap.put(null, 'Jared Dunn');

System.debug('Value of studentsMap = ' + studentsMap);
System.debug('Total number of elements inside studentsMap = ' + studentsMap.size());

// * Getting value from a map
System.debug('Student with roll number 3 = ' + studentsMap.get(3));

// * Updating value inside a map
System.debug('Assigning a new name to roll number 3');
studentsMap.put(3, 'Gavin Belson');

System.debug('Student with roll number 3 = ' + studentsMap.get(3));
System.debug('Value of studentsMap = ' + studentsMap);

// * Removing value from a map
studentsMap.remove(3);
System.debug('Value of studentsMap after removing student with roll number 3 = ' + studentsMap);
System.debug('Total number of elements inside studentsMap = ' + studentsMap.size());

// * Map - Part 2

Map<Integer, String> studentsMap = new Map<Integer, String>();
studentsMap.put(5, 'Monica');
studentsMap.put(1, 'Richard Hendricks');
studentsMap.put(2, 'Dinesh');
studentsMap.put(4, 'Erlich Bachman');
studentsMap.put(null, 'Jared Dunn');

// * Check if the map contains a key
System.debug('Does studentsMap contain roll number 4? ' + studentsMap.containsKey(4));
System.debug('Does studentsMap contain roll number 3? ' + studentsMap.containsKey(3));

System.debug('Value of studentsMap = ' + studentsMap);
System.debug('Total number of elements inside studentsMap = ' + studentsMap.size());

// * Check if map is empty
System.debug('Is student map empty? ' + studentsMap.isEmpty());

// * Remove all elements from the map
System.debug('Clearing elements inside studentsMap...');
studentsMap.clear();

// * Check if map is empty
System.debug('Is student map empty? ' + studentsMap.isEmpty());

System.debug('Value of studentsMap = ' + studentsMap);
System.debug('Total number of elements inside studentsMap = ' + studentsMap.size());

// * Getting KeySet and Values from the map
Map<Integer, String> studentsMap = new Map<Integer, String>();
studentsMap.put(1, 'Richard Hendricks');
studentsMap.put(2, 'Dinesh');
studentsMap.put(3, 'Gilfoyle');
studentsMap.put(4, 'Erlich Bachman');
studentsMap.put(2, 'Monica');
studentsMap.put(6, 'Dinesh');

System.debug('Value of studentsMap = ' + studentsMap);
System.debug('Total number of elements inside studentsMap = ' + studentsMap.size());

Set<Integer> keys = studentsMap.keySet();
System.debug('Keys of studentsMap = ' + keys);

List<String> studentNames = studentsMap.values();
System.debug('Values of studentsMap = ' + studentNames);

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