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Java Digital Clock Using Swing with explanation of code

written by 75ypsaw71

In this tutorial, we'll create a simple digital clock in Java using the Swing framework. The clock will display the current time and update every second.

This is a great way to learn about GUI programming in Java, handling time, and updating the user interface dynamically.

Here is what we will create and you can see some of the code in the background.

We can also think about other features and how we add them to our clock or modify our clocks appearance. Lets carry on.

Table of Contents

Features of the Digital Clock:

Displays the current time in HH:mm format.
Updates every second to show the accurate current time.
Uses Swing components like JFrame, JLabel, and Timer.
Provides a clean and simple user interface.

Complete Code of the Digital Clock

import javax.swing.*;
import java.awt.*;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DigitalClock extends JFrame {

    private JLabel timeLabel;
    private SimpleDateFormat timeFormat;

    public DigitalClock() {
        // Set up the frame
        this.setTitle("Digital Clock");
        this.setSize(300, 150);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setLocationRelativeTo(null); // Center the frame

        // Set up the time format
        timeFormat = new SimpleDateFormat("HH:mm:ss");

        // Create a label to display the time
        timeLabel = new JLabel();
        timeLabel.setFont(new Font("Verdana", Font.PLAIN, 50));
        timeLabel.setHorizontalAlignment(SwingConstants.CENTER);

        // Add the label to the frame
        this.add(timeLabel);

        // Create a timer to update the time every second
        Timer timer = new Timer(1000, e -> updateTime());
        timer.setInitialDelay(0);
        timer.start();

        // Make the frame visible
        this.setVisible(true);
    }

    private void updateTime() {
        // Get the current time and set it to the label
        String currentTime = timeFormat.format(new Date());
        timeLabel.setText(currentTime);
    }

    public static void main(String[] args) {
        // Run the clock in the Event Dispatch Thread
        SwingUtilities.invokeLater(() -> new DigitalClock());
    }
}

Explanation of the Code

1. Import Statements

import javax.swing.*;
import java.awt.*;
import java.text.SimpleDateFormat;
import java.util.Date;
javax.swing.*: Imports all Swing components needed for the GUI (JFrame, JLabel, Timer, etc.).
java.awt.*: Imports AWT classes for graphics (Font, Color, etc.).
java.text.SimpleDateFormat: Allows formatting of date and time.
java.util.Date: Provides date and time information.

2. Class Declaration

public class DigitalClock extends JFrame {
    // Class content
}

DigitalClock extends JFrame, making it a window that can contain GUI components.

3. Instance Variables

private JLabel timeLabel;
private SimpleDateFormat timeFormat;
timeLabel: Displays the current time.
timeFormat: Defines the format in which the time will be displayed.

4. Constructor

public DigitalClock() {
    // Frame setup
    this.setTitle("Digital Clock");
    this.setSize(300, 150);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setLocationRelativeTo(null);

    // Time format setup
    timeFormat = new SimpleDateFormat("HH:mm:ss");

    // Time label setup
    timeLabel = new JLabel();
    timeLabel.setFont(new Font("Verdana", Font.PLAIN, 50));
    timeLabel.setHorizontalAlignment(SwingConstants.CENTER);

    // Adding label to frame
    this.add(timeLabel);

    // Timer setup
    Timer timer = new Timer(1000, e -> updateTime());
    timer.setInitialDelay(0);
    timer.start();

    // Making the frame visible
    this.setVisible(true);
}

Frame Setup:

setTitle(“Digital Clock”): Sets the window title.
setSize(300, 150): Sets the window size.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE): Closes the application when the window is closed.
setLocationRelativeTo(null): Centers the window on the screen.

Time Format Setup:

timeFormat = new SimpleDateFormat(“HH:mm:ss”): Defines the time format (24-hour format).

Time Label Setup:

timeLabel = new JLabel(): Initializes the label.
setFont(new Font(“Verdana”, Font.PLAIN, 50)): Sets the font type and size.
setHorizontalAlignment(SwingConstants.CENTER): Centers the text in the label.

Adding Label to Frame:

this.add(timeLabel): Adds the label to the frame.
Timer Setup:

Timer timer = new Timer(1000, e -> updateTime()): Creates a timer that triggers every 1000 milliseconds (1 second) and calls updateTime().
setInitialDelay(0): Starts the timer immediately without delay.
timer.start(): Starts the timer.

Making Frame Visible:

this.setVisible(true): Displays the window.

5. updateTime() Method

private void updateTime() {
    String currentTime = timeFormat.format(new Date());
    timeLabel.setText(currentTime);
}

Gets the current time using new Date().
Formats the time according to timeFormat.
Updates the label to display the current time.

6. main() Method

public static void main(String[] args) {
    SwingUtilities.invokeLater(() -> new DigitalClock());
}

Ensures thread safety by running GUI updates on the Event Dispatch Thread.
Creates an instance of DigitalClock, which sets up and displays the clock.

Step-by-Step Breakdown

Initialize the Frame:

We set up the main window (JFrame) for our digital clock.
Define Time Format:

We specify how the time will be displayed using SimpleDateFormat.
Create and Configure the Time Label:

We create a JLabel to show the time.
We set its font and alignment for better visibility.
Add the Label to the Frame:

The label is added to the frame so it will be displayed.
Set Up the Timer:

A Timer is created to update the time every second.
The updateTime() method is called every time the timer ticks.
Display the Frame:

We make the frame visible so the user can see the clock.
Update Time Method:

This method gets the current time and updates the label.
It is called by the timer every second.
Run the Application:

The main() method launches the application safely on the Event Dispatch Thread.

Enhancements and Customizations

1. Displaying the Date

You can modify the code to also display the current date.

Changes:

Add another JLabel for the date.
Update the updateTime() method to set the date.
Modified Code Snippet:

private JLabel dateLabel;
private SimpleDateFormat dateFormat;

public DigitalClock() {
    // ... existing code ...

    // Set up the date format
    dateFormat = new SimpleDateFormat("EEEE, MMMM dd, yyyy");

    // Create a label to display the date
    dateLabel = new JLabel();
    dateLabel.setFont(new Font("Verdana", Font.PLAIN, 25));
    dateLabel.setHorizontalAlignment(SwingConstants.CENTER);

    // Add labels to the frame using a layout manager
    this.setLayout(new GridLayout(2, 1));
    this.add(timeLabel);
    this.add(dateLabel);

    // ... existing code ...
}

private void updateTime() {
    String currentTime = timeFormat.format(new Date());
    String currentDate = dateFormat.format(new Date());
    timeLabel.setText(currentTime);
    dateLabel.setText(currentDate);
}

2. Changing to 12-Hour Format

To display time in a 12-hour format with AM/PM:

Change the time format pattern.

Modified Code Snippet:

timeFormat = new SimpleDateFormat("hh:mm:ss a");

3. Customizing Appearance

Change Fonts: Use different fonts or styles.
Change Colors: Set background and foreground colors.

Example:

timeLabel.setForeground(Color.BLUE);
timeLabel.setBackground(Color.BLACK);
timeLabel.setOpaque(true);

Running the Application

To compile and run the application:

Save the code in a file named DigitalClock.java.

Compile the code using the command:

javac DigitalClock.java

Run the application using the command:

java DigitalClock

Note: Ensure that your Java Development Kit (JDK) is properly installed and configured.

Conclusion

By following this tutorial, you've created a functional digital clock using Java Swing.

This example demonstrates:

Creating a GUI application with Swing components.
Using Timer to perform actions at regular intervals.
Formatting dates and times with SimpleDateFormat.
Ensuring thread safety in Swing applications by using the Event Dispatch Thread.

You can further enhance this digital clock by adding new features like:

Alarm functionality.
Custom skins or themes.
Resizable fonts based on window size.
Additional time zones.

This project serves as a solid foundation for learning GUI programming in Java and can be expanded upon for more complex applications.

October 10, 2024 0 comment

Code

Java Calculator Tutorial with code explained

written by 75ypsaw71

In this tutorial, we will build a simple calculator in Java that can perform basic arithmetic operations such as addition, subtraction, multiplication, division, and modulus.

We will use the command-line interface to interact with the user, allowing them to input numbers and choose an operation.

Table of Contents

Features of the Calculator:

The user will input two numbers.
The user will choose the operation (add, subtract, multiply, divide, modulus).
The calculator will perform the operation and display the result.
The user will be able to perform multiple operations in a loop until they decide to exit.

Code for the Calculator

import java.util.Scanner;

public class Calculator {

    // Method to display the menu
    public static void displayMenu() {
        System.out.println("---- Calculator Menu ----");
        System.out.println("1. Add");
        System.out.println("2. Subtract");
        System.out.println("3. Multiply");
        System.out.println("4. Divide");
        System.out.println("5. Modulus");
        System.out.println("6. Exit");
        System.out.print("Choose an operation: ");
    }

    // Method to perform the calculation
    public static void calculate(double num1, double num2, int operation) {
        switch (operation) {
            case 1:
                System.out.println("Result: " + (num1 + num2));
                break;
            case 2:
                System.out.println("Result: " + (num1 - num2));
                break;
            case 3:
                System.out.println("Result: " + (num1 * num2));
                break;
            case 4:
                if (num2 != 0) {
                    System.out.println("Result: " + (num1 / num2));
                } else {
                    System.out.println("Error: Division by zero is undefined.");
                }
                break;
            case 5:
                if (num2 != 0) {
                    System.out.println("Result: " + (num1 % num2));
                } else {
                    System.out.println("Error: Modulus by zero is undefined.");
                }
                break;
            default:
                System.out.println("Invalid operation.");
                break;
        }
    }

    // Main method
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // Main program loop
        while (true) {
            displayMenu(); // Display menu
            int operation = scanner.nextInt(); // Read operation from user

            // If user chooses to exit, break the loop
            if (operation == 6) {
                System.out.println("Exiting calculator. Goodbye!");
                break;
            }

            // Get numbers from user
            System.out.print("Enter the first number: ");
            double num1 = scanner.nextDouble();

            System.out.print("Enter the second number: ");
            double num2 = scanner.nextDouble();

            // Perform the calculation based on the user's choice
            calculate(num1, num2, operation);
            System.out.println(); // Print a blank line for readability
        }

        scanner.close(); // Close the scanner
    }
}

Explanation of the Code:

1. Main Method

public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);

    // Main program loop
    while (true) {
        displayMenu(); // Display menu
        int operation = scanner.nextInt(); // Read operation from user

        // If user chooses to exit, break the loop
        if (operation == 6) {
            System.out.println("Exiting calculator. Goodbye!");
            break;
        }

        // Get numbers from user
        System.out.print("Enter the first number: ");
        double num1 = scanner.nextDouble();

        System.out.print("Enter the second number: ");
        double num2 = scanner.nextDouble();

        // Perform the calculation based on the user's choice
        calculate(num1, num2, operation);
        System.out.println(); // Print a blank line for readability
    }

    scanner.close(); // Close the scanner
}

Scanner Object: We create a Scanner object to take input from the user.
Main Program Loop: The program runs in an infinite loop (while(true)) to continuously prompt the user for inputs and operations. The loop continues until the user selects the “Exit” option (6).
Menu Display: The displayMenu() method is called to show the user the available options for arithmetic operations.
Operation Input: The user selects an operation by entering a number (1 to 6).
Number Input: The user inputs two numbers (num1 and num2) which will be used for the chosen operation.
Exiting the Program: If the user selects 6 (Exit), the program exits the loop and closes the scanner.

2. Menu Display

public static void displayMenu() {
    System.out.println("---- Calculator Menu ----");
    System.out.println("1. Add");
    System.out.println("2. Subtract");
    System.out.println("3. Multiply");
    System.out.println("4. Divide");
    System.out.println("5. Modulus");
    System.out.println("6. Exit");
    System.out.print("Choose an operation: ");
}

Menu Options: This method displays the available operations (Addition, Subtraction, Multiplication, Division, Modulus) and an option to exit.
Operation Input Prompt: The user is prompted to choose an operation by entering a number (1 to 6).

3. Calculate Method

public static void calculate(double num1, double num2, int operation) {
    switch (operation) {
        case 1:
            System.out.println("Result: " + (num1 + num2));
            break;
        case 2:
            System.out.println("Result: " + (num1 - num2));
            break;
        case 3:
            System.out.println("Result: " + (num1 * num2));
            break;
        case 4:
            if (num2 != 0) {
                System.out.println("Result: " + (num1 / num2));
            } else {
                System.out.println("Error: Division by zero is undefined.");
            }
            break;
        case 5:
            if (num2 != 0) {
                System.out.println("Result: " + (num1 % num2));
            } else {
                System.out.println("Error: Modulus by zero is undefined.");
            }
            break;
        default:
            System.out.println("Invalid operation.");
            break;
    }
}

Switch Statement: This method uses a switch statement to handle the various operations based on the user's input (operation):
Addition: Adds num1 and num2 and prints the result.
Subtraction: Subtracts num2 from num1 and prints the result.
Multiplication: Multiplies num1 by num2 and prints the result.
Division: Divides num1 by num2 if num2 is not zero. If num2 is zero, an error message is displayed since division by zero is undefined.
Modulus: Computes the modulus (remainder) of num1 divided by num2 if num2 is not zero. If num2 is zero, an error message is displayed.
Error Handling: For division and modulus, we check whether the second number (num2) is zero to prevent runtime errors.

Example Run of the Program

---- Calculator Menu ----
1. Add
2. Subtract
3. Multiply
4. Divide
5. Modulus
6. Exit
Choose an operation:
1

Enter the first number:
10

Enter the second number:
5

Result: 15.0

---- Calculator Menu ----
1. Add
2. Subtract
3. Multiply
4. Divide
5. Modulus
6. Exit
Choose an operation:
2

Enter the first number:
12

Enter the second number:
4

Result: 8.0

---- Calculator Menu ----
1. Add
2. Subtract
3. Multiply
4. Divide
5. Modulus
6. Exit
Choose an operation:
6

Exiting calculator. Goodbye!

Customizing the Calculator

You can extend or modify this basic calculator by adding more features, such as:

Exponentiation (power).
Square root calculation.
Scientific functions like sine, cosine, and tangent.
Support for multiple inputs and more complex expressions.

Conclusion

This basic Java calculator program demonstrates how to use fundamental Java concepts like loops, conditionals, methods, and input handling.

The program structure allows the user to continuously perform calculations until they choose to exit, making it interactive and easy to extend with additional features.

By following this tutorial, you have built a simple calculator that can perform basic arithmetic operations and handle division by zero errors.

You can further expand it to include more advanced operations or a graphical user interface (GUI) using Java Swing for a more advanced calculator experience.

October 10, 2024 0 comment

Code

Java Riddle Game with explanation

written by 75ypsaw71

In this tutorial, we will build a simple riddle game in Java. The game will ask the user a series of riddles, and the user will have a limited number of attempts to guess the answer correctly.

If the user answers correctly, they score a point. If they run out of attempts, they will lose the round and the correct answer will be displayed.

Table of Contents

Features of the Game:

The game will have a set of riddles stored in an array or list.
The user will be prompted to answer each riddle.
The user has a limited number of attempts (e.g., 3 attempts) to answer each riddle.
If the user guesses correctly, they earn points.
After all riddles have been answered, the game will display the final score.

Complete code

import java.util.Scanner;

public class RiddleGame {

    // Array of riddles
    private static String[] riddles = {
        "I speak without a mouth and hear without ears. I have no body, but I come alive with wind. What am I?",
        "You measure my life in hours, and I serve you by expiring. I'm quick when I'm thin and slow when I'm fat. What am I?",
        "The more of this there is, the less you see. What is it?"
    };

    // Corresponding array of answers
    private static String[] answers = {
        "echo",
        "candle",
        "darkness"
    };

    // Number of attempts allowed for each riddle
    private static final int MAX_ATTEMPTS = 3;

    // Method to start the game
    public static void startGame() {
        Scanner scanner = new Scanner(System.in);
        int score = 0; // Initialize the player's score

        // Loop through all riddles
        for (int i = 0; i < riddles.length; i++) {
            System.out.println("Riddle " + (i + 1) + ": " + riddles[i]);
            boolean answeredCorrectly = false;

            // Give the user multiple attempts to answer
            for (int attempt = 1; attempt <= MAX_ATTEMPTS; attempt++) {
                System.out.print("Attempt " + attempt + " of " + MAX_ATTEMPTS + ": ");
                String userAnswer = scanner.nextLine().trim().toLowerCase();

                // Check if the user's answer is correct
                if (userAnswer.equals(answers[i])) {
                    System.out.println("Correct! You've earned 1 point.\n");
                    score++; // Increment score for a correct answer
                    answeredCorrectly = true;
                    break; // Exit the loop if the answer is correct
                } else {
                    System.out.println("Wrong answer.");
                }
            }

            // If the user fails to answer correctly after all attempts
            if (!answeredCorrectly) {
                System.out.println("You've used all attempts. The correct answer was: " + answers[i] + "\n");
            }
        }

        // Display the user's final score after all riddles
        System.out.println("Game Over! Your final score is: " + score + "/" + riddles.length);
        scanner.close();
    }

    // Main method
    public static void main(String[] args) {
        System.out.println("Welcome to the Riddle Game!");
        startGame();
    }
}

Explanation of the Code:

1. Array of Riddles and Answers

private static String[] riddles = {
    "I speak without a mouth and hear without ears. I have no body, but I come alive with wind. What am I?",
    "You measure my life in hours, and I serve you by expiring. I'm quick when I'm thin and slow when I'm fat. What am I?",
    "The more of this there is, the less you see. What is it?"
};

private static String[] answers = {
    "echo",
    "candle",
    "darkness"
};

We define two arrays: one for the riddles and one for their corresponding answers. The indexes of the riddle and its answer match, so riddles[0] has the answer answers[0].

2. MAX_ATTEMPTS Constant

private static final int MAX_ATTEMPTS = 3;
This constant defines the maximum number of attempts the user will have for each riddle. In this case, the user gets 3 attempts to guess the correct answer.

3. The startGame Method

public static void startGame() {
    Scanner scanner = new Scanner(System.in);
    int score = 0; // Initialize the player's score

    // Loop through all riddles
    for (int i = 0; i < riddles.length; i++) {
        System.out.println("Riddle " + (i + 1) + ": " + riddles[i]);
        boolean answeredCorrectly = false;

        // Give the user multiple attempts to answer
        for (int attempt = 1; attempt <= MAX_ATTEMPTS; attempt++) {
            System.out.print("Attempt " + attempt + " of " + MAX_ATTEMPTS + ": ");
            String userAnswer = scanner.nextLine().trim().toLowerCase();

            // Check if the user's answer is correct
            if (userAnswer.equals(answers[i])) {
                System.out.println("Correct! You've earned 1 point.\n");
                score++; // Increment score for a correct answer
                answeredCorrectly = true;
                break; // Exit the loop if the answer is correct
            } else {
                System.out.println("Wrong answer.");
            }
        }

        // If the user fails to answer correctly after all attempts
        if (!answeredCorrectly) {
            System.out.println("You've used all attempts. The correct answer was: " + answers[i] + "\n");
        }
    }

    // Display the user's final score after all riddles
    System.out.println("Game Over! Your final score is: " + score + "/" + riddles.length);
    scanner.close();
}

Score Initialization: A variable score is initialized to keep track of the user’s correct answers.
Looping through Riddles: The game loops through the riddles array, displaying one riddle at a time.
Multiple Attempts: For each riddle, a nested loop allows the user to attempt answering the riddle up to MAX_ATTEMPTS times.
If the user’s answer is correct (matches the corresponding answers[i]), the score is incremented, and the loop breaks.
If the user fails to answer within the given attempts, the correct answer is revealed.
Final Score: After all the riddles have been asked, the game displays the user's final score.

4. Main Method

public static void main(String[] args) {
    System.out.println("Welcome to the Riddle Game!");
    startGame();
}

The main() method is where the game begins. It prints a welcome message and calls the startGame() method to run the game logic.

Game Flow

The game starts with a welcome message.
The game presents the first riddle and gives the user three attempts to answer.
If the user answers correctly within three attempts, they earn a point.
If they fail to answer correctly, the correct answer is shown.
This process repeats for all riddles.
After all the riddles are answered, the game ends and displays the user's score.

Example Run:

Welcome to the Riddle Game!
Riddle 1: I speak without a mouth and hear without ears. I have no body, but I come alive with wind. What am I?
Attempt 1 of 3: wind
Wrong answer.
Attempt 2 of 3: sound
Wrong answer.
Attempt 3 of 3: echo
Correct! You've earned 1 point.

Riddle 2: You measure my life in hours, and I serve you by expiring. I'm quick when I'm thin and slow when I'm fat. What am I?
Attempt 1 of 3: candle
Correct! You've earned 1 point.

Riddle 3: The more of this there is, the less you see. What is it?
Attempt 1 of 3: light
Wrong answer.
Attempt 2 of 3: darkness
Correct! You've earned 1 point.

Game Over! Your final score is: 3/3

Modifying the Game

Adding more riddles: You can easily add more riddles by adding more entries to the riddles and answers arrays.
Changing the number of attempts: The number of attempts can be adjusted by changing the value of MAX_ATTEMPTS.
Enhancing the game: You could extend the game by adding features like difficulty levels, a timer, or randomizing the order of riddles.

Conclusion

This simple riddle game demonstrates how to use Java loops, conditionals, and input handling to create an interactive console-based game.

The game structure can be extended and modified to suit more advanced needs, but this version covers the basics of interactivity and scoring in a fun and engaging way.

October 10, 2024 0 comment

Code

Another 25 simple Java code examples

written by 75ypsaw71

In this article we give you another 25 simple Java code examples that cover various programming concepts like control structures, loops, arrays, methods, and object-oriented programming.

We always find that actually trying out code examples and running them is one of the best ways to learn a new language

Table of Contents

26. Generate Random Number

import java.util.Random;
public class RandomNumber {
    public static void main(String[] args) {
        Random rand = new Random();
        int randomNum = rand.nextInt(100); // Random number between 0 and 99
        System.out.println("Random number: " + randomNum);
    }
}

27. Print a Triangle Pattern

public class TrianglePattern {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            for (int j = 1; j <= i; j++) {
                System.out.print("* ");
            }
            System.out.println();
        }
    }
}

28. Simple Calculator Using Switch

import java.util.Scanner;
public class Calculator {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter first number: ");
        int num1 = sc.nextInt();
        System.out.print("Enter second number: ");
        int num2 = sc.nextInt();
        System.out.print("Enter operation (+, -, *, /): ");
        char op = sc.next().charAt(0);
        switch (op) {
            case '+':
                System.out.println("Result: " + (num1 + num2));
                break;
            case '-':
                System.out.println("Result: " + (num1 - num2));
                break;
            case '*':
                System.out.println("Result: " + (num1 * num2));
                break;
            case '/':
                System.out.println("Result: " + (num1 / num2));
                break;
            default:
                System.out.println("Invalid operation");
        }
        sc.close();
    }
}

29. Find Power of a Number

public class PowerOfNumber {
    public static void main(String[] args) {
        int base = 2, exponent = 3;
        int result = 1;
        for (int i = 0; i < exponent; i++) {
            result *= base;
        }
        System.out.println("Result: " + result);
    }
}

30. Find Average of Array Elements

public class AverageArray {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        int sum = 0;
        for (int num : arr) {
            sum += num;
        }
        double average = (double) sum / arr.length;
        System.out.println("Average: " + average);
    }
}

31. Count Occurrence of Character in String

public class CountCharacter {
    public static void main(String[] args) {
        String str = "hello world";
        char target = 'l';
        int count = 0;
        for (char c : str.toCharArray()) {
            if (c == target) {
                count++;
            }
        }
        System.out.println("Occurrence of '" + target + "': " + count);
    }
}

32. Check if a String is a Palindrome

public class PalindromeString {
    public static void main(String[] args) {
        String str = "madam";
        String rev = new StringBuilder(str).reverse().toString();
        if (str.equals(rev)) {
            System.out.println(str + " is a palindrome");
        } else {
            System.out.println(str + " is not a palindrome");
        }
    }
}

33. Find Second Largest Number in Array

public class SecondLargest {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        int largest = Integer.MIN_VALUE, secondLargest = Integer.MIN_VALUE;
        for (int num : arr) {
            if (num > largest) {
                secondLargest = largest;
                largest = num;
            } else if (num > secondLargest && num != largest) {
                secondLargest = num;
            }
        }
        System.out.println("Second largest: " + secondLargest);
    }
}

34. Count Occurrence of Word in Sentence

public class WordCount {
    public static void main(String[] args) {
        String sentence = "Java is fun and Java is powerful";
        String word = "Java";
        int count = 0;
        String[] words = sentence.split(" ");
        for (String w : words) {
            if (w.equalsIgnoreCase(word)) {
                count++;
            }
        }
        System.out.println("Occurrence of word '" + word + "': " + count);
    }
}

35. Sum of Elements in a Matrix

public class MatrixSum {
    public static void main(String[] args) {
        int[][] matrix = {
            {1, 2, 3},
            {4, 5, 6},
            {7, 8, 9}
        };
        int sum = 0;
        for (int[] row : matrix) {
            for (int element : row) {
                sum += element;
            }
        }
        System.out.println("Sum of matrix elements: " + sum);
    }
}

36. Transpose of a Matrix

public class TransposeMatrix {
    public static void main(String[] args) {
        int[][] matrix = {
            {1, 2, 3},
            {4, 5, 6}
        };
        int[][] transpose = new int[matrix[0].length][matrix.length];
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix[i].length; j++) {
                transpose[j][i] = matrix[i][j];
            }
        }
        for (int[] row : transpose) {
            for (int element : row) {
                System.out.print(element + " ");
            }
            System.out.println();
        }
    }
}

37. Count Positive and Negative Numbers in Array

public class CountPositiveNegative {
    public static void main(String[] args) {
        int[] arr = {1, -2, 3, -4, 5};
        int positiveCount = 0, negativeCount = 0;
        for (int num : arr) {
            if (num > 0) {
                positiveCount++;
            } else if (num < 0) {
                negativeCount++;
            }
        }
        System.out.println("Positive numbers: " + positiveCount);
        System.out.println("Negative numbers: " + negativeCount);
    }
}

38. Find Sum of Diagonal Elements in Matrix

public class DiagonalSum {
    public static void main(String[] args) {
        int[][] matrix = {
            {1, 2, 3},
            {4, 5, 6},
            {7, 8, 9}
        };
        int sum = 0;
        for (int i = 0; i < matrix.length; i++) {
            sum += matrix[i][i];
        }
        System.out.println("Sum of diagonal elements: " + sum);
    }
}

39. Find Intersection of Two Arrays

import java.util.HashSet;
public class Intersection {
    public static void main(String[] args) {
        int[] arr1 = {1, 2, 3, 4, 5};
        int[] arr2 = {4, 5, 6, 7, 8};
        HashSet set = new HashSet<>();
        for (int num : arr1) {
            set.add(num);
        }
        System.out.print("Intersection: ");
        for (int num : arr2) {
            if (set.contains(num)) {
                System.out.print(num + " ");
            }
        }
    }
}

40. Find Union of Two Arrays

import java.util.HashSet;
public class Union {
    public static void main(String[] args) {
        int[] arr1 = {1, 2, 3, 4, 5};
        int[] arr2 = {4, 5, 6, 7, 8};
        HashSet set = new HashSet<>();
        for (int num : arr1) {
            set.add(num);
        }
        for (int num : arr2) {
            set.add(num);
        }
        System.out.print("Union: ");
        for (int num : set) {
            System.out.print(num + " ");
        }
    }
}

41. Count Words in a Sentence

public class WordCounter {
    public static void main(String[] args) {
        String sentence = "Java programming is fun";
        String[] words = sentence.split(" ");
        System.out.println("Number of words: " + words.length);
    }
}

42. Check if Two Strings are Anagrams

import java.util.Arrays;
public class AnagramCheck {
    public static void main(String[] args) {
        String str1 = "listen", str2 = "silent";
        char[] arr1 = str1.toCharArray();
        char[] arr2 = str2.toCharArray();
        Arrays.sort(arr1);
        Arrays.sort(arr2);
        if (Arrays.equals(arr1, arr2)) {
            System.out.println(str1 + " and " + str2 + " are anagrams");
        } else {
            System.out.println(str1 + " and " + str2 + " are not anagrams");
        }
    }
}

43. Check if a Matrix is Symmetric

public class SymmetricMatrix {
    public static void main(String[] args) {
        int[][] matrix = {
            {1, 2, 3},
            {2, 4, 5},
            {3, 5, 6}
        };
        boolean isSymmetric = true;
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix.length; j++) {
                if (matrix[i][j] != matrix[j][i]) {
                    isSymmetric = false;
                    break;
                }
            }
        }
        if (isSymmetric) {
            System.out.println("The matrix is symmetric");
        } else {
            System.out.println("The matrix is not symmetric");
        }
    }
}

44. Find Duplicate Elements in Array

import java.util.HashSet;
public class FindDuplicates {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 2, 5, 1};
        HashSet set = new HashSet<>();
        System.out.print("Duplicates: ");
        for (int num : arr) {
            if (!set.add(num)) {
                System.out.print(num + " ");
            }
        }
    }
}

45. Find Substring in String

public class SubstringCheck {
    public static void main(String[] args) {
        String str = "Hello World";
        String sub = "World";
        if (str.contains(sub)) {
            System.out.println(sub + " is a substring of " + str);
        } else {
            System.out.println(sub + " is not a substring of " + str);
        }
    }
}

46. Reverse Words in a Sentence

public class ReverseWords {
    public static void main(String[] args) {
        String sentence = "Java is fun";
        String[] words = sentence.split(" ");
        String reversedSentence = "";
        for (int i = words.length - 1; i >= 0; i--) {
            reversedSentence += words[i] + " ";
        }
        System.out.println("Reversed: " + reversedSentence.trim());
    }
}

47. Convert String to Uppercase

public class StringToUpperCase {
    public static void main(String[] args) {
        String str = "hello";
        String upperStr = str.toUpperCase();
        System.out.println("Uppercase: " + upperStr);
    }
}

48. Find the Sum of Natural Numbers

public class SumOfNaturalNumbers {
    public static void main(String[] args) {
        int num = 10, sum = 0;
        for (int i = 1; i <= num; i++) {
            sum += i;
        }
        System.out.println("Sum: " + sum);
    }
}

49. Remove Duplicates from Array

import java.util.HashSet;
public class RemoveDuplicates {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 2, 5, 1};
        HashSet set = new HashSet<>();
        System.out.print("Array without duplicates: ");
        for (int num : arr) {
            if (set.add(num)) {
                System.out.print(num + " ");
            }
        }
    }
}

50. Find the Largest Element in Array

public class LargestElement {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        int largest = arr[0];
        for (int num : arr) {
            if (num > largest) {
                largest = num;
            }
        }
        System.out.println("Largest element: " + largest);
    }
}

These examples touch upon basic programming concepts, string manipulation, array operations, and algorithms that will help you gain a solid understanding of Java fundamentals.

October 9, 2024 0 comment

Code

25 simple Java code examples

written by 75ypsaw71

In this article we give you 25 simple Java code examples that cover various programming concepts like control structures, loops, arrays, methods, and object-oriented programming.

We always find that actually trying out code examples and running them is one of the best ways to learn a new language

1. Hello World

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

2. Sum of Two Numbers

public class Sum {
    public static void main(String[] args) {
        int a = 5, b = 10;
        int sum = a + b;
        System.out.println("Sum: " + sum);
    }
}

3. Check Even or Odd

public class EvenOdd {
    public static void main(String[] args) {
        int num = 10;
        if (num % 2 == 0) {
            System.out.println(num + " is even");
        } else {
            System.out.println(num + " is odd");
        }
    }
}

4. Find Largest Number

public class LargestNumber {
    public static void main(String[] args) {
        int a = 5, b = 10, c = 3;
        if (a > b && a > c) {
            System.out.println("Largest is: " + a);
        } else if (b > c) {
            System.out.println("Largest is: " + b);
        } else {
            System.out.println("Largest is: " + c);
        }
    }
}

5. Factorial of a Number

public class Factorial {
    public static void main(String[] args) {
        int num = 5;
        int fact = 1;
        for (int i = 1; i <= num; i++) {
            fact *= i;
        }
        System.out.println("Factorial: " + fact);
    }
}

6. Fibonacci Series

public class Fibonacci {
    public static void main(String[] args) {
        int a = 0, b = 1, n = 10;
        System.out.print(a + " " + b);
        for (int i = 2; i < n; i++) {
            int next = a + b;
            System.out.print(" " + next);
            a = b;
            b = next;
        }
    }
}

7. Reverse a String

public class ReverseString {
    public static void main(String[] args) {
        String str = "Hello";
        String rev = "";
        for (int i = str.length() - 1; i >= 0; i--) {
            rev += str.charAt(i);
        }
        System.out.println("Reversed: " + rev);
    }
}

8. Prime Number Check

public class PrimeCheck {
    public static void main(String[] args) {
        int num = 29;
        boolean isPrime = true;
        for (int i = 2; i <= num / 2; i++) {
            if (num % i == 0) {
                isPrime = false;
                break;
            }
        }
        if (isPrime) {
            System.out.println(num + " is prime");
        } else {
            System.out.println(num + " is not prime");
        }
    }
}

9. Sum of Array Elements

public class SumArray {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        int sum = 0;
        for (int num : arr) {
            sum += num;
        }
        System.out.println("Sum: " + sum);
    }
}

10. Swap Two Variables

public class Swap {
    public static void main(String[] args) {
        int a = 5, b = 10;
        System.out.println("Before swap: a = " + a + ", b = " + b);
        int temp = a;
        a = b;
        b = temp;
        System.out.println("After swap: a = " + a + ", b = " + b);
    }
}

11. Multiplication Table

public class MultiplicationTable {
    public static void main(String[] args) {
        int num = 5;
        for (int i = 1; i <= 10; i++) {
            System.out.println(num + " x " + i + " = " + num * i);
        }
    }
}

12. Armstrong Number

public class ArmstrongNumber {
    public static void main(String[] args) {
        int num = 153, sum = 0, temp = num;
        while (temp != 0) {
            int digit = temp % 10;
            sum += Math.pow(digit, 3);
            temp /= 10;
        }
        if (sum == num) {
            System.out.println(num + " is an Armstrong number");
        } else {
            System.out.println(num + " is not an Armstrong number");
        }
    }
}

13. Sum of Digits

public class SumOfDigits {
    public static void main(String[] args) {
        int num = 1234, sum = 0;
        while (num != 0) {
            sum += num % 10;
            num /= 10;
        }
        System.out.println("Sum of digits: " + sum);
    }
}

14. Reverse a Number

public class ReverseNumber {
    public static void main(String[] args) {
        int num = 1234, reversed = 0;
        while (num != 0) {
            int digit = num % 10;
            reversed = reversed * 10 + digit;
            num /= 10;
        }
        System.out.println("Reversed: " + reversed);
    }
}

15. GCD of Two Numbers

public class GCD {
    public static void main(String[] args) {
        int a = 54, b = 24;
        while (b != 0) {
            int temp = b;
            b = a % b;
            a = temp;
        }
        System.out.println("GCD: " + a);
    }
}

16. LCM of Two Numbers

public class LCM {
    public static void main(String[] args) {
        int a = 54, b = 24, gcd = 1;
        for (int i = 1; i <= a && i <= b; i++) {
            if (a % i == 0 && b % i == 0) {
                gcd = i;
            }
        }
        int lcm = (a * b) / gcd;
        System.out.println("LCM: " + lcm);
    }
}

17. Leap Year Check

public class LeapYear {
    public static void main(String[] args) {
        int year = 2024;
        if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
            System.out.println(year + " is a leap year");
        } else {
            System.out.println(year + " is not a leap year");
        }
    }
}

18. Count Vowels in a String

public class VowelCount {
    public static void main(String[] args) {
        String str = "Hello World";
        int count = 0;
        for (char c : str.toCharArray()) {
            if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u') {
                count++;
            }
        }
        System.out.println("Vowel count: " + count);
    }
}

19. Find Length of a String

public class StringLength {
    public static void main(String[] args) {
        String str = "Hello World";
        System.out.println("Length: " + str.length());
    }
}

20. Convert Binary to Decimal

public class BinaryToDecimal {
    public static void main(String[] args) {
        String binary = "1010";
        int decimal = Integer.parseInt(binary, 2);
        System.out.println("Decimal: " + decimal);
    }
}

21. Convert Decimal to Binary

public class DecimalToBinary {
    public static void main(String[] args) {
        int decimal = 10;
        String binary = Integer.toBinaryString(decimal);
        System.out.println("Binary: " + binary);
    }
}

22. Find ASCII Value of a Character

public class ASCIIValue {
    public static void main(String[] args) {
        char c = 'A';
        int ascii = (int) c;
        System.out.println("ASCII value: " + ascii);
    }
}

23. Print Numbers from 1 to 10

public class PrintNumbers {
    public static void main(String[] args) {
        for (int i = 1; i <= 10; i++) {
            System.out.println(i);
        }
    }
}

24. Find Minimum and Maximum in an Array

public class MinMaxArray {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        int min = arr[0], max = arr[0];
        for (int num : arr) {
            if (num < min) { min = num; } if (num > max) {
                max = num;
            }
        }
        System.out.println("Min: " + min + ", Max: " + max);
    }
}

25. Check if a Number is Palindrome

public class Palindrome {
    public static void main(String[] args) {
        int num = 121, reversed = 0, original = num;
        while (num != 0) {
            int digit = num % 10;
            reversed = reversed * 10 + digit;
            num /= 10;
        }
        if (original == reversed) {
            System.out.println(original + " is a palindrome");
        } else {
            System.out.println(original + " is not a palindrome");
        }
    }
}

October 9, 2024 0 comment

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