Expert Tips for Interviews & Certifications
A class is a blueprint that defines behavior (methods) and data (variables).
A class is like a recipe, and methods are the steps.
public class Car {
public void drive() {
System.debug('Car is moving');
}
}
A method is a function inside a class that performs an action.
Car myCar = new Car(); myCar.drive();
Classes group logic, methods perform actions.
Access modifiers control who can access a class, method, or variable.
public – Accessible within org
private – Accessible only inside class
protected – Accessible in subclass
global – Accessible everywhere (used in APIs)
Think of access modifiers like house access:
private → bedroom
public → living room
global → front gate
public class AccountService {
private Integer count;
}
Access modifiers control visibility and security.
Belong to an object
Require object creation
Car car1 = new Car();
Belong to the class
No object required
public class MathUtil {
public static Integer add(Integer a, Integer b) {
return a + b;
}
}
Integer sum = MathUtil.add(5, 3);
Static = Class-level
Instance = Object-level
Static members don’t need objects; instance members do.
A constructor initializes an object when it is created.
public class Student {
public String name;
public Student(String studentName) {
name = studentName;
}
}
Method overloading allows multiple methods with the same name but different parameters.
public Integer add(Integer a, Integer b) {
return a + b;
}
public Integer add(Integer a, Integer b, Integer c) {
return a + b + c;
}
Same button, different functions based on input.
Constructors set values; overloading adds flexibility.
An inner class is a class defined inside another class.
Group related logic
Improve code organization
Hide implementation details
public class OuterClass {
public class InnerClass {
public void show() {
System.debug('Inside Inner Class');
}
}
}
Inner classes help organize and encapsulate related logic.
