Java Programming Examples

Posted on Oct 17, 2024 in Computers

Sorting an ArrayList in Descending Order

Code Example

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class ArrayListSortDescending {
    public static void main(String[] args) {
        // Create an ArrayList to store Integer elements
        ArrayList<Integer> list = new ArrayList<>();

        // Create a Scanner object for input
        Scanner scanner = new Scanner(System.in);

        // Prompt user to enter the number of elements
        System.out.print("Enter the number of elements you want to add: ");
        int numberOfElements = scanner.nextInt();

        // Prompt user to enter the elements
        System.out.println("Enter the elements:");
        for (int i = 0; i < numberOfElements; i++) {
            int element = scanner.nextInt();
            list.add(element);
        }

        // Sort the list in descending order using Collections.reverseOrder()
        Collections.sort(list, Collections.reverseOrder());

        // Display the sorted list
        System.out.println("Sorted list in descending order:");
        for (int element : list) {
            System.out.println(element);
        }

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

Creating Singleton Collections

Code Example

import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class SingletonCollectionExample {
    public static void main(String[] args) {
        // Create a singleton set
        Set<String> singletonSet = Collections.singleton("singleElement");
        System.out.println("Singleton Set: " + singletonSet);

        // Create a singleton list
        List<String> singletonList = Collections.singletonList("singleElement");
        System.out.println("Singleton List: " + singletonList);

        // Create a singleton map
        Map<String, String> singletonMap = Collections.singletonMap("key", "value");
        System.out.println("Singleton Map: " + singletonMap);
    }
}

Creating Unmodifiable Collections

Code Example

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class UnmodifiableCollectionExample {
    public static void main(String[] args) {
        // Create a modifiable list
        List<String> modifiableList = new ArrayList<>();
        modifiableList.add("element1");
        modifiableList.add("element2");

        // Create an unmodifiable view of the list
        List<String> unmodifiableList = Collections.unmodifiableList(modifiableList);
        System.out.println("Unmodifiable List: " + unmodifiableList);

        // Attempting to modify the unmodifiable list will throw an exception
        try {
            unmodifiableList.add("element3");
        } catch (UnsupportedOperationException e) {
            System.out.println("Cannot modify an unmodifiable list: " + e);
        }

        // However, modifications to the original list are reflected in the unmodifiable view
        modifiableList.add("element3");
        System.out.println("Unmodifiable List after modifying the original list: " + unmodifiableList);
    }
}

Drawing a Circle with JavaFX

Code Example

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;

public class CircleInSceneExample extends Application {
    @Override
    public void start(Stage primaryStage) {
        // Create a Circle
        Circle circle = new Circle(50); // Radius of 50
        circle.setFill(Color.RED); // Fill the circle with red color

        // Create a layout container (StackPane) and add the circle to it
        StackPane root = new StackPane();
        root.getChildren().add(circle);

        // Create a Scene with the StackPane as the root node
        Scene scene = new Scene(root, 300, 200); // 300x200 scene size

        // Set the scene in the stage
        primaryStage.setScene(scene);
        primaryStage.setTitle("Circle in Scene Example");
        primaryStage.show(); // Display the stage
    }

    public static void main(String[] args) {
        launch(args); // Launch the JavaFX application
    }
}

Handling Events with JavaFX

Code Example

// ... (rest of the provided code examples) ...