Java is a versatile and widely-used programming language known for its portability and platform independence. In this Markdown document, we will explore various Java concepts with a plethora of real-world examples to help you understand the language better.
Table of Contents
- Hello, World!
- Variables and Data Types
- Conditional Statements
- Loops
- Arrays
- Functions (Methods)
- Object-Oriented Programming
- File Handling
Hello, World!
public class HelloWorld {
public static void main(String[] args) {
// This is a simple Java program that prints "Hello, World!" to the console.
System.out.println("Hello, World!");
}
}
In this example, we have a Java program that consists of a class named HelloWorld. The main method is the entry point for the program, and it prints "Hello, World!" to the console using System.out.println.
Variables and Data Types
public class VariablesExample {
public static void main(String[] args) {
// Declare and initialize variables
int age = 25;
double salary = 50000.50;
String name = "John Doe";
// Print variable values
System.out.println("Name: " + name);
System.out.println("Age: " + age);
System.out.println("Salary: " + salary);
}
}
In this example, we declare and initialize variables of different data types (int, double, and String). Then, we print the values of these variables to the console.
Conditional Statements (If-Else Statement)
public class IfElseExample {
public static void main(String[] args) {
// Define an age
int age = 18;
// Check if the age is greater than or equal to 18
if (age >= 18) {
System.out.println("You are an adult.");
} else {
System.out.println("You are not yet an adult.");
}
}
}
In this example, we use an if-else statement to check whether a person is an adult based on their age. If the age is greater than or equal to 18, it prints "You are an adult"; otherwise, it prints "You are not yet an adult."
Loops (For Loop)
public class ForLoopExample {
public static void main(String[] args) {
// Use a for loop to count from 1 to 5
for (int i = 1; i <= 5; i++) {
System.out.println("Count: " + i);
}
}
}
This example demonstrates a for loop that counts from 1 to 5 and prints the count at each iteration. The loop initializes i to 1, continues as long as i is less than or equal to 5, and increments i by 1 in each iteration.
Loops (While Loop)
public class WhileLoopExample {
public static void main(String[] args) {
// Use a while loop to count from 1 to 5
int i = 1;
while (i <= 5) {
System.out.println("Count: " + i);
i++;
}
}
}
This example uses a while loop to achieve the same counting from 1 to 5 as the previous example. It initializes i to 1, and the loop continues as long as i is less than or equal to 5. In each iteration, it prints the count and increments i.
Arrays
public class ArrayExample {
public static void main(String[] args) {
// Declare and initialize an integer array
int[] numbers = {1, 2, 3, 4, 5};
// Access and print array elements
System.out.println("Element at index 0: " + numbers[0]);
System.out.println("Element at index 2: " + numbers[2]);
// Calculate and print the length of the array
int length = numbers.length;
System.out.println("Array length: " + length);
}
}
In this example, we declare and initialize an integer array called numbers. We access and print specific elements of the array using their indices (e.g., numbers[0] and numbers[2]). We also calculate and print the length of the array using numbers.length.
Functions (Methods)
public class MethodsExample {
// Define a method to calculate the sum of two numbers
public static int add(int a, int b) {
return a + b;
}
public static void main(String[] args) {
// Call the 'add' method and print the result
int result = add(5, 3);
System.out.println("Sum: " + result);
}
}
In this example, we define a method (add) that takes two integer parameters and returns their sum. In the main method, we call the add method with values 5 and 3, and then we print the result.
Object-Oriented Programming (Classes and Objects)
// Define a class named 'Person'
class Person {
String name;
int age;
// Constructor to initialize 'name' and 'age'
public Person(String name, int age) {
this.name = name;
this.age = age;
}
// Method to display person information
public void displayInfo() {
System.out.println("Name: " + name);
System.out.println("Age: " + age);
}
}
public class OOPExample {
public static void main(String[] args) {
// Create objects of the 'Person' class
Person person1 = new Person("Alice", 25);
Person person2 = new Person("Bob", 30);
// Call the 'displayInfo' method for each person
person1.displayInfo();
person2.displayInfo();
}
}
In this example, we define a class called Person with attributes (name and age) and a constructor to initialize them. We also define a method (displayInfo) to display the person's information. In the main method, we create two Person objects, set their attributes, and call the displayInfo method for each object.
File Handling (Reading and Writing)
import java.io.*;
public class FileHandlingExample {
public static void main(String[] args) {
try {
// Create a FileWriter to write to a file
FileWriter writer = new FileWriter("sample.txt");
writer.write("Hello, File Handling!");
writer.close();
// Create a FileReader to read from the file
FileReader reader = new FileReader("sample.txt");
int character;
while ((character = reader.read()) != -1) {
System.out.print((char) character);
}
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
In this example, we demonstrate basic file handling in Java. We use a FileWriter to write the string "Hello, File Handling!" to a file named "sample.txt" and a FileReader to read and print the contents of the same file.
These additional examples cover arrays, methods, object-oriented programming (classes and objects), and file handling in Java. If you have any specific questions or if you'd like to see more examples related to a particular topic, please feel free to ask.
Top comments (3)
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Thank you