user_input.java

// UserInput.java
import java.util.Scanner;

public class UserInput {
    private Scanner scanner;

    public UserInput(Scanner scanner) {
        this.scanner = scanner;
    }

    public void handleChoice(int choice, Calculator calculator) {
        switch (choice) {
            case 1: case 2: case 3: case 4:
                System.out.println("Enter two numbers: ");
                double num1 = scanner.nextDouble();
                double num2 = scanner.nextDouble();
                performBasicOperation(choice, num1, num2, calculator);
                break;
            case 5:
                System.out.println("Enter Fibonacci index: ");
                int n = scanner.nextInt();
                System.out.println("Fibonacci(" + n + ") = " + calculator.fibonacci(n));
                break;
            case 6: case 7: case 8: case 9:
                System.out.println("Enter array size: ");
                int size = scanner.nextInt();
                double[] array = new double[size];
                System.out.println("Enter elements: ");
                for (int i = 0; i < size; i++) {
                    array[i] = scanner.nextDouble();
                }
                performArrayOperation(choice, array, calculator);
                break;
            default:
                System.out.println("Invalid choice!");
        }
    }

    private void performBasicOperation(int choice, double a, double b, Calculator calculator) {
        switch (choice) {
            case 1: System.out.println("Result: " + calculator.add(a, b)); break;
            case 2: System.out.println("Result: " + calculator.subtract(a, b)); break;
            case 3: System.out.println("Result: " + calculator.multiply(a, b)); break;
            case 4: System.out.println("Result: " + calculator.divide(a, b)); break;
        }
    }

    private void performArrayOperation(int choice, double[] array, Calculator calculator) {
        switch (choice) {
            case 6: System.out.println("Sum: " + calculator.sumArray(array)); break;
            case 7: System.out.println("Mean: " + calculator.mean(array)); break;
            case 8: System.out.println("Variance: " + calculator.variance(array)); break;
            case 9: System.out.println("Standard Deviation: " + calculator.standardDeviation(array)); break;
        }
    }
}