How are the main concepts of object-oriented programming implemented in Java?

In Java, the main concepts of object-oriented programming (OOP) are implemented as follows:

• Encapsulation: achieved through access modifiers (private, protected, public) and access methods (getters and setters), which hide the internal data of a class and provide controlled access.

• Inheritance: implemented using the extends keyword, allowing the creation of a new class based on an existing one, inheriting its fields and methods.

• Polymorphism: achieved through method overriding and using references to the base class for objects of derived classes. It allows using a single interface for different implementations.

• Abstraction: implemented using abstract classes (abstract class) and interfaces (interface), which define a behavior template without a specific implementation.

Example:

// Abstract class
abstract class Animal {
    abstract void sound(); // abstract method
}

// Inheritance and polymorphism
class Dog extends Animal {
    @Override
    void sound() {
        System.out.println("Woof");
    }
}

public class Main {
    public static void main(String[] args) {
        Animal myDog = new Dog(); // polymorphism
        myDog.sound(); // calls Dog's method
    }
}

Thus, Java provides syntax and mechanisms to implement all key principles of OOP.