Zack Tech Blog

Java Program package LAB_Report; /* 2. Write a program in Java to demonstrate the usage of access modifiers: public, private, protected and default. */ class AccessModifier{ int defaultValue ; // this is visible within the package only public int publicValue ; // this is visible everywhere protected int protectedValue ; // this is visible within the package and subclasses private int privateValue ; // this is visible within the class only public void setPrivateValue ( int privateValue) { this . privateValue = privateValue; } public int getPrivateValue () { return privateValue ; } } class AccessModifierProtected extends AccessModifier{ public void setValue ( int value2){ this . protectedValue = value2; } public int getValue2 (){ return protectedValue ; } } public class Lab_2 { public static void main (String[] args) { AccessModifier am = new AccessModifier(); ...

  Inheritance is one of the fundamental concepts of Object-Oriented Programming (OOP) in Java. It allows a new class (child or subclass) to inherit the properties and behaviors (fields and methods) of an existing class (parent or superclass). This promotes code reuse and establishes a natural hierarchical relationship between classes. Types of Inheritance in Java Single Inheritance: A class inherits from one superclass. Multilevel Inheritance: A class inherits from another class, which in turn inherits from another class. Hierarchical Inheritance: Multiple classes inherit from one superclass. Note: Java does not support multiple inheritance (a class inheriting from more than one class) directly to avoid complexity and ambiguity. However, it can be achieved using interfaces. Examples of Inheritance Single Inheritance In single inheritance, a class inherits from one superclass. // Parent class class Vehicle { String brand = "Ford" ; void honk () { S...

Introduction Network Address Translation (NAT) is a fundamental technique used in networking to translate private IP addresses to public IP addresses and vice versa. Static NAT is a method where a specific private IP address is mapped to a specific public IP address.  Configuration Steps Router Configuration Enable NAT Service Router(config)# ip nat inside source static [inside-local] [inside-global] Replace [inside-local] with the private IP address to be translated. Replace [inside-global] with the public IP address to translate to. Configure Interfaces Router(config)# interface [inside-interface] Router(config-if)# ip address [inside-ip-address] [subnet-mask] Router(config-if)# ip nat inside Router(config-if)# no shutdown Router(config-if)# exit Router(config)# interface [outside-interface] Router(config-if)# ip address [outside-ip-address] [subnet-mask] Router(config-if)# ip nat outside Router(config-if)# no shutdown Router(config-if)# exit Replace [inside-interf...

What is the static Keyword? In Java, the static keyword is used to indicate that a particular member (variable or method) belongs to the class itself, rather than to instances of the class. This means that the static member can be accessed without creating an instance of the class. Static Variables A static variable is shared among all instances of a class. It is also known as a class variable. Example: public class Example { // static variable static int count = 0 ; Example() { count++; } public static void main (String[] args) { Example obj1 = new Example (); Example obj2 = new Example (); Example obj3 = new Example (); System.out.println( "Count: " + Example.count); // Output: Count: 3 } } In this example, the count variable is static and shared among all instances of the Example class. It keeps track of the number of instances created. Static Methods A static method belongs to ...

  What is a Method? In Java, a method is a block of code that performs a specific task. Methods are used to define the behavior of objects created from a class. They encapsulate code that can be reused and invoked whenever needed, making programs more modular and manageable. Defining a Method A method consists of a method declaration and a method body. The method declaration provides the method's name, return type, and parameters, while the method body contains the code to be executed. Syntax: returnType methodName (parameters) { // method body } Example: public class Example { // Method to add two numbers public int add ( int a, int b) { return a + b; } public static void main (String[] args) { Example example = new Example (); int sum = example.add( 5 , 3 ); System.out.println( "Sum: " + sum); // Output: Sum: 8 } } Method Components Access Modifiers: Define the visibility of the method (e....

  What is a Constructor? In Java, a constructor is a special block of code similar to a method. It is called when an instance of the class is created. The primary purpose of a constructor is to initialize the newly created object. When a constructor is invoked, memory for the object is allocated in the memory. Every time an object is created using the new() keyword, at least one constructor is called. Java provides a default constructor if no constructor is explicitly defined in the class. Characteristics of a Constructor Initialization: A constructor initializes the object. Invocation: Called automatically when a new object is created. Default Constructor: If no constructor is defined, Java provides a default constructor. Rules for Creating a Java Constructor Constructor Name: Must be the same as the class name. Return Type: Must not have an explicit return type. Modifiers: Cannot be abstract, static, final, or synchronized. Note: Access modifiers can be used to control ob...

What is an Object? An object is an entity that possesses both state and behavior. In simple terms, an object is an instance of a class. It encapsulates the properties (state) and functionalities (behavior) defined by its class.  Example: Object: Pencil State:   Name: Ballpoint   Color: Black Behavior:   - To write  What is a Class? A class is a blueprint for creating objects. It defines a set of properties and methods that the created objects will have. Think of a class as a template that outlines what an object will be like. Components of a Class: Fields: Variables to store data. Methods: Functions to define behaviors. Constructors: Special methods to initialize objects. Blocks: Code blocks for initialization. Nested Class and Interface: Classes or interfaces defined within another class Instance Variables Instance variables are variables declared within a class but outside any method. They are specific to each object created from the class. Unlike static varia...