Apex Classes & Objects
In Apex (like other object-oriented languages), a class is a blueprint for creating objects. It defines the properties (called variables or fields) and behaviors (called methods or functions) of real-world entities.
An object is a specific instance of a class that holds real values for the properties defined in the class.
1. Creating a Class
A class in Apex starts with the class keyword followed by the class name.
Syntax:
public class ClassName {
// Properties (Variables)
// Methods (Functions)
}
2. Creating an Object from a Class
An object is a real-world version of a class. It’s created using the new keyword.
Syntax:
ClassName objectName = new ClassName();
Examples
Student s1 = new Student();
s1.name = ‘Adnan’;
s1.age = 22;
s1.displayDetails();
Code Explaination
• Student is the class (blueprint).
• s1 is the object (a real student created from the blueprint).
• We assign values using the dot (.) operator: s1.name = ‘Adnan’.
• Then we call a method: s1.displayDetails() to print the data.
Real-Life Analogy: "Class vs Object"
• A class is like the design of a mobile phone model. An object is the real phone in your hand built from that design.
You can create many phones (objects) from one design (class).
Code Example
1: Simple Class with Properties and Method
public class Student {
public String name;
public Integer age;
public void displayInfo() {
System.debug(‘Name: ‘ + name);
System.debug(‘Age: ‘ + age);
}
}
Student s1 = new Student();
s1.name = ‘Adnan’;
s1.age = 22;
Code Explaination
• public class Student – defines a class named Student.
• name and age – variables that store info about a student.
• displayInfo() – method that prints the student’s info.
• Student s1 = new Student() – creates an object of the Student class.
• s1.name = ‘Adnan’ – assigns value to the object’s variable.
• s1.displayInfo() – calls the method to print the data.
Output:
Name: Adnan Age: 22
2: Class with Constructor
A constructor is a special method that runs automatically when the object is created.
public class Car {
public String brand;
public Integer year;
// Constructor
public Car(String b, Integer y) {
brand = b;
year = y;
}
public void showDetails() {
System.debug(‘Brand: ‘ + brand);
System.debug(‘Year: ‘ + year);
}
}
Car c1 = new Car(‘Toyota’, 2022);
c1.showDetails();
Code Explaination
• Car(String b, Integer y) – constructor that initializes brand and year.
• c1 is created and initialized in one step: new Car(‘Toyota’, 2022).
• .showDetails() displays the values.
Output:
Brand: Toyota
Year: 2022
3: Method that Returns a Value
public class Calculator {
public Integer add(Integer a, Integer b) {
return a + b;
}
}
Calculator calc = new Calculator();
Integer result = calc.add(10, 20);
System.debug(‘Sum is: ‘ + result);
Code Explanation:
• Method add() takes two numbers and returns their sum.
• calc.add(10, 20) returns 30.
• Output is printed using System.debug.
Output:
Sum is :30
Tasks for Practice
Task 1: Create a class Book with title, author, and a method printDetails(). Create an object and print the book details.
Task 2: Create a class Employee with a constructor that accepts name and salary. Print the details.
Task 3: Create a class Rectangle with length and width. Add a method calculateArea() that returns the area.
Task 4: Create a class Calculator with methods: add, subtract, multiply, divide. Call each method and print the result.
Task 5: Create a class Movie with title, genre, and rating. Create an object and write a method isRecommended() that returns true if the rating is more than 8.
Task 6: Create a class called Book with the following properties:
• String title
• String author
• Double price Then, create an object of the class and print its values.
Task 7: Create two classes:
• Greeting class with a method sayHello() that prints “Hello, Salesforce Learner!”
• MainClass with the mainMethod() where you create a Greeting object and call its method.
