What is the difference between a class, an object, and an interface in Java?

A class is a blueprint for creating objects, defining their state (fields) and behavior (methods). An object (instance of a class) is a specific realization of the class in memory with a unique state. An interface is a contract, a fully abstract type that defines a set of methods that must be implemented by classes that implement it.

Property	Class	Object	Interface
Entity	Template	Instance of a class	Contract
State	Can have fields (state)	Has specific field values	Fields are only static final
Behavior	Can have methods (behavior)	Executes methods defined by the class	Defines method signatures
Abstraction	Can be abstract	Not abstract	Fully abstract
Multiple inheritance	No	No	Yes (multiple implementation)
Creation	Created using the class keyword	Created using the new keyword	Created using the interface keyword

Example:

// Class: template for creating cars
class Car {
    String model; // Field (state)

    // Method (behavior)
    void start() {
        System.out.println(model + " started.");
    }
}

// Object: a specific car
Car myCar = new Car(); // Creating an object
myCar.model = "Toyota"; // Assigning state
myCar.start(); // Calling behavior

// Interface: contract for objects that can drive
interface Drivable {
    void drive(); // Defines method signature
}

// Class implementing the interface
class Truck implements Drivable {
    @Override
    public void drive() {
        System.out.println("Truck is driving.");
    }
}

// Example of using the interface
Drivable vehicle = new Truck();
vehicle.drive();