Object Oriented Programming Using JAVA

The `Object` class in Java serves as the root of the class hierarchy. Here are some key points to understand about the `Object` class along with examples: 1. Default Superclass: If a class doesn't extend any other class explicitly, it implicitly inherits from the `Object` class.    public class MyClass {        // MyClass inherits from Object implicitly    } 2. toString() Method: Provides a string representation of the object. It is commonly overridden to return meaningful information about the object.    public class Student {        private String name;        private int age;        // Constructor and other methods...        @Override        public String toString() {            return "Student{name='" + name + "', age=" + age + '}';        }    } 3. equals() Method: Compares...

Dynamic method dispatch is a mechanism in Java where the method to be executed is determined at runtime rather than at compile time. It is also known as runtime polymorphism or late binding. In Java, dynamic method dispatch is achieved through method overriding, where a subclass provides a specific implementation of a method that is already present in its superclass. When a method is invoked on an object, the JVM determines which version of the method to execute based on the actual type of the object at runtime. Here's how dynamic method dispatch works: 1. Method Override: Subclasses can override methods defined in their superclass to provide specialized implementations. The subclass method must have the same signature (name and parameters) as the superclass method. 2. Runtime Binding: When a method is called on an object, the JVM determines the appropriate method implementation to execute based on the actual type of the object at runtime. 3. Polymorphic Behavior: Dynamic method...

In Java, interfaces can extend other interfaces, enabling interface inheritance. This allows one interface to inherit the methods and constants of another interface. The child interface inherits all the abstract methods, default methods, and static methods of the parent interface. Syntax: interface ParentInterface {     // Methods and constants } interface ChildInterface extends ParentInterface {     // Additional methods and constants } Example: interface Animal {     void eat(); } interface Dog extends Animal {     void bark(); } class Labrador implements Dog {     public void eat() {         System.out.println("Labrador is eating");     }     public void bark() {         System.out.println("Labrador is barking");     } } public class Main {     public static void main(String[] args) {         Labrador labrador = new Labrador();   ...

In Java, the `instanceof` operator is used to check whether an object is an instance of a particular class or implements a particular interface. It returns `true` if the object is an instance of the specified class or implements the specified interface; otherwise, it returns `false`. Syntax: object instanceof ClassName or object instanceof InterfaceName - `object`: The object whose type is to be checked. - `ClassName`: The name of the class. - `InterfaceName`: The name of the interface. Example: class Animal {} class Dog extends Animal {} class Cat extends Animal {} public class Main {     public static void main(String[] args) {         Animal a = new Dog();         System.out.println(a instanceof Animal); // true         System.out.println(a instanceof Dog);    // true         System.out.println(a instanceof Cat);    // false     } } In this example: - `a instanceof ...

In Java, an interface reference variable can be used to refer to objects of classes that implement the interface. This allows for polymorphism and flexibility in designing code. Here's how it works: 1. Declaring Interface Reference:    MyInterface obj;    Here, `MyInterface` is the interface, and `obj` is a reference variable of type `MyInterface`. 2. Assigning Objects:     obj = new MyClass(); // MyClass implements MyInterface    The `obj` reference variable can point to any object of a class that implements the `MyInterface` interface. 3. Accessing Methods:    obj.method(); // Calls method() implemented in MyClass    Through the interface reference variable, you can call methods declared in the interface. The actual implementation of the method depends on the class to which `obj` is currently referring. Example: // Interface definition interface MyInterface {     void method(); } // Class implementing the interface ...

Interface in Java: In Java, an interface is a reference type that defines a set of abstract methods without providing implementations. It serves as a contract that classes can implement to guarantee that they provide certain functionality. Interfaces can also contain constant fields, default methods, static methods, and nested types. Here's an overview of interfaces in Java: 1. Declaring Interfaces: Interfaces are declared using the `interface` keyword, followed by the interface name and a set of abstract method declarations. Here's an example: public interface Animal {     void eat();   // Abstract method declaration     void sleep(); // Abstract method declaration } 2. Implementing Interfaces: A class implements an interface by providing concrete implementations for all the abstract methods declared in the interface. Use the `implements` keyword to indicate that a class implements an interface. Here's an example: public class Dog implements Animal { ...

 In Java, the `final` keyword is used to restrict the ability to modify entities such as variables, methods, and classes. Here's a breakdown of how `final` is used in different contexts: 1. Final Variables:    - When applied to a variable, it indicates that the variable's value cannot be changed once it has been initialized.    - Final instance variables must be initialized before the constructor completes or through an instance initializer block.    - Final static variables (class variables) must be initialized before the class is loaded, either through direct assignment or within a static initializer block.    public class MyClass {        final int x = 10; // final instance variable        final static int y; // final static variable        static {            y = 20; // initialization of final static variable        }   ...