Object Oriented Programming Using JAVA

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Showing posts with the label Lab Experiments

Understanding Constructors in Java: A Simple Guide with Examples and Analogies

What is a Constructor in Java? In Java, a constructor is a special type of method that is used to initialize objects. When you create an object of a class, the constructor is called automatically. Its main job is to set the initial values of the object’s properties or perform any setup that the object needs before it can be used. Why Do We Need Constructors? You need constructors because: Initialization : Constructors are responsible for initializing an object when it is created. Automatic Execution : A constructor is automatically called when an object is created, so you don’t have to manually initialize every property. Simplifying Object Creation : It simplifies object creation by providing default values or custom initialization. Where Do Constructors Fit in Java? Constructors fit within a class. They are used whenever a new object of that class is created, and they allow the object to be initialized. Constructors must have the same name as the class, and they don't have a re...

Implementing Arrays and String Functions in Java

1️⃣ Working with Arrays in Java An array in Java is a collection of elements of the same type , stored in contiguous memory locations. 🔹 Declaring and Initializing an Array: public class ArrayExample { public static void main (String[] args) { int [] numbers = { 10 , 20 , 30 , 40 , 50 }; // Array declaration and initialization System.out.println( "First element: " + numbers[ 0 ]); // Accessing array elements // Using a loop to print all elements System.out.println( "Array Elements:" ); for ( int num : numbers) { System.out.println(num); } } } ✅ Output: First element: 10 Array Elements: 10 20 30 40 50 🔹 Taking Array Input from User and Finding Sum: import java.util.Scanner; public class ArrayInput { public static void main (String[] args) { Scanner sc = new Scanner (System.in); System.out.print( "Enter number of elemen...

Why is String[] args necessary in main() method in Java?

Why is String[] args necessary in main() method in Java? In Java, the main method serves as the entry point for the program. The correct syntax for the main method is: public static void main (String[] args) { System.out.println( "Hello, Java!" ); } 🔹 Breaking it down: public → Accessible from anywhere. static → No need to create an object of the class to run it. void → No return value. main → Special method recognized by the JVM as the starting point. String[] args → Stores command-line arguments (optional but required by JVM). Why Can't We Skip String[] args ? JVM looks for main(String[] args) When you run a Java program, the JVM searches for the main method with exactly this signature : public static void main (String[] args) If you change or remove String[] args , the JVM cannot find the correct main() method and throws a runtime error (NoSuchMethodError). Java Specification Requires It The Java Language Specification (JLS) defines that main...

Reading Values from Keyboard in Java

Reading Values from Keyboard in Java In Java, we can take user input from the keyboard using different methods. The most common ways are: Using Scanner Class (Recommended) Using BufferedReader Using Console Class 1. Using Scanner Class (Most Common & Easy) The Scanner class is the easiest way to read input from the keyboard. It is part of the java.util package. Example: Read Integer, Float, and String Input import java.util.Scanner; // Import Scanner class public class ScannerExample { public static void main (String[] args) { Scanner sc = new Scanner (System.in); // Create Scanner object System.out.print( "Enter your name: " ); String name = sc.nextLine(); // Read String input System.out.print( "Enter your age: " ); int age = sc.nextInt(); // Read integer input System.out.print( "Enter your salary: " ); float salary = sc.nextFloat(); // Re...

Basic Java Program for Operators, Variables, and Control Flow Statements

1. Variables and Operators in Java A variable is used to store data, and operators perform operations on these variables. Example: Arithmetic Operators public class BasicOperators { public static void main (String[] args) { int a = 10 , b = 5 ; System.out.println( "Sum: " + (a + b)); System.out.println( "Difference: " + (a - b)); System.out.println( "Product: " + (a * b)); System.out.println( "Quotient: " + (a / b)); System.out.println( "Remainder: " + (a % b)); } } Explanation: + (Addition), - (Subtraction), * (Multiplication), / (Division), % (Modulo) are used to perform arithmetic calculations. 2. Control Flow Statements in Java Control flow statements decide the execution path of the program based on conditions. Example: If-Else Statement public class IfElseExample { public static void main (String[] args) { int num = 10 ; ...

Experiment No: 1 - Study of Java Runtime Environment (JRE).

Experiment No: 1 Aim: Study of Java run time environment (JRE) Theory: Java is a programming language and a platform. Platform Any hardware or software environment in which a program runs, known as a platform. Since Java has its own Runtime Environment (JRE) and API, it is called platform. The history of Java is a fascinating journey that began in the early 1990s and continues to shape the modern software development landscape. Here's an overview of the key milestones and events in the history of Java: Origins (Early 1990s): Java's story begins with a team of engineers at Sun Microsystems, led by James Gosling, Mike Sheridan, and Patrick Naughton. Their goal was to create a programming language that could be used to develop software for consumer electronic devices, such as set-top boxes and interactive television. Green Project (1991): The project, initially known as the "Green Project," aimed to develop a language that could addr...