Java Logical Operations

Java supports standard arithmetic operations including addition, subtraction, multiplication, division, modulus, and increment/decrement:

int num1 = 3;
int num2 = 5;
long num3 = 8;
float num4 = 6.6f;
double num5 = 9.321;
String greeting = "Hello, ";

int total = num1 + num2;
System.out.println(total);

System.out.println(num1 + num3);
System.out.println(num1 / num4);
System.out.println(num4 * num5);
System.out.println(greeting + num1);
System.out.println(num3 % num1);
System.out.println(num1++);
System.out.println(++num2);

Conditional Statements

Java provides several ways to implement conditional logic:

// Boolean expressions
System.out.println(num1 == num1);
System.out.println(num1 == num2);
System.out.println(num1 % num2 == num3);

// If-else statement
if(num1 == 3) {
    System.out.println("num1 equals 3");
} else {
    System.out.println("num1 doesn't equal 3");
}

// Switch-case statement
switch(num1) {
    case 1:
        System.out.println("num1 is 1");
        break;
    case 2:
        System.out.println("num1 is 2");
        break;
    case 3:
        System.out.println("num1 is 3");
        break;
    default:
        System.out.println("num1 is not 1, 2, or 3");
        break;
}

Looping Constructs

Java offers multiple loop structures:

// For loop
for(int counter = 0; counter < 10; counter++) {
    System.out.println("For loop iteration: " + counter);
}

// While loop
int countdown = 10;
while(countdown > 0) {
    countdown--;
    System.out.println("While loop count: " + countdown);
}

Essential Utility Classes

1. Input/Output with Scanner:

Scanner reader = new Scanner(System.in);
String userInput = reader.next();
System.out.println(userInput);

2. String manipulation methods
3. Date and time operations
4. Number formatting
5. Math class functions
6. Exception handling mechanisms

Data Structures

Arrays

String[] colors = new String[10];
colors[0] = "red";
colors[1] = "blue";
System.out.println(colors[0]);

for(String color : colors) {
    System.out.println(color);
}

Lists

List<String> fruits = new ArrayList<>();
fruits.add("apple");
fruits.add("banana");
System.out.println(fruits.get(0));

Maps

Map<String, String> capitals = new HashMap<>();
capitals.put("France", "Paris");
capitals.put("Germany", "Berlin");
System.out.println(capitals.containsKey("Germany"));
System.out.println(capitals.get("Germany"));

File Operations

import java.io.FileInputStream;
import java.io.FileOutputStream;

public class FileHandler {
    public static String readFile(String path) throws Exception {
        FileInputStream input = new FileInputStream(path);
        byte[] data = new byte[input.available()];
        input.read(data);
        input.close();
        return new String(data);
    }

    public static void writeFile(String content, String path) throws Exception {
        FileOutputStream output = new FileOutputStream(path);
        output.write(content.getBytes());
        output.flush();
        output.close();
    }
}

Object-Oriented Principles

Encapsulation

Encapsulation bundles data and methods within a class while controllling access through interfaces. Benefits include:

1. Reduced coupling between components
2. Flexible internal implementation
3. Controlled member access
4. Information hiding

Inheritance

public class Vehicle {
    protected String model;
    protected String vin;
    
    public void startEngine() {
        System.out.println("Engine started");
    }
}

public class Car extends Vehicle {
    public void displayInfo() {
        System.out.println(this.model);
        System.out.println(this.vin);
        this.startEngine();
    }
}

Polymorphism

public class Animal {
    public void move() {
        System.out.println("Animal moving");
    }
}

public class Bird extends Animal {
    @Override
    public void move() {
        System.out.println("Bird flying");
    }
}

public class Fish extends Animal {
    @Override
    public void move() {
        System.out.println("Fish swimming");
    }
}