Java

Some sample Java code snippets that cover the most common and essential parts of Java programming, useful for beginners and intermediate level.

1. Variables and Data Types

// Java variable declarations
int age = 25;
double price = 19.99;
boolean isStudent = true;
char grade = 'A';
String name = "Alice";

System.out.println("Name: " + name + ", Age: " + age);
    

2. Conditional Statements

int number = 10;

if (number > 0) {
    System.out.println("Positive");
} else if (number < 0) {
    System.out.println("Negative");
} else {
    System.out.println("Zero");
}
    

3. Switch Statement

char grade = 'B';

switch (grade) {
    case 'A':
        System.out.println("Excellent!");
        break;
    case 'B':
        System.out.println("Well done");
        break;
    case 'C':
        System.out.println("Good");
        break;
    default:
        System.out.println("Needs improvement");
}
    

4. Loops (for, while, do-while)

// For loop
for (int i = 1; i <= 5; i++) {
    System.out.println("Count: " + i);
}

// While loop
int j = 1;
while (j <= 5) {
    System.out.println("While: " + j);
    j++;
}

// Do-while loop
int k = 1;
do {
    System.out.println("Do-while: " + k);
    k++;
} while (k <= 5);
    

5. Arrays

int[] numbers = {10, 20, 30, 40, 50};

for (int num : numbers) {
    System.out.println("Value: " + num);
}
    

6. Methods (Functions)

public class Calculator {
    public static int add(int a, int b) {
        return a + b;
    }

    public static void main(String[] args) {
        int result = add(5, 3);
        System.out.println("Sum: " + result);
    }
}
    

7. Classes and Objects

class Person {
    String name;
    int age;

    void introduce() {
        System.out.println("Hi, I'm " + name + " and I'm " + age + " years old.");
    }
}

public class Main {
    public static void main(String[] args) {
        Person p = new Person();
        p.name = "Bob";
        p.age = 30;
        p.introduce();
    }
}
    

8. Exception Handling

public class ErrorDemo {
    public static void main(String[] args) {
        try {
            int result = 10 / 0;
            System.out.println("Result: " + result);
        } catch (ArithmeticException e) {
            System.out.println("Error: Division by zero");
        } finally {
            System.out.println("This always runs");
        }
    }
}
    

9. String Operations

String text = "Hello, World!";
System.out.println(text.toUpperCase());  // HELLO, WORLD!
System.out.println(text.length());       // 13
System.out.println(text.contains("World")); // true
    

10. Simple Class with Constructor

class Car {
    String model;

    Car(String m) {
        model = m;
    }

    void drive() {
        System.out.println("Driving " + model);
    }
}

public class Main {
    public static void main(String[] args) {
        Car car = new Car("Toyota");
        car.drive();
    }
}
    

These examples should give a foundational understanding of core Java features. Build on these by exploring inheritance, interfaces, collections, file I/O, and more.