How to close keyboard

And still have the program accept input once the program completes one time.

I get resource leak warnings for the keyboard, but the program keeps accepting new input.

If I close the keyboard.close(), the warning goes away, but the program must be restarted after each run.

// Created by Paul A. Gureghian in Sept 2020.
// This Java program calculates the area of 3 different shapes, Triangle, Rectangle, Circle.

// Import modules 
import java.util.*;

// Define a class
public class AreaCalculator {

    // Define the main function
    public static void main(String[] args) {

        Scanner keyboard = new Scanner(System.in);

        System.out.println("\n Shape Area Calculator \n");

        while (true) {

            System.out.println();
            System.out.println("-=-=-=-=-=-=-=-=-=-");
            System.out.println();
            System.out.println("1) Triangle");
            System.out.println("2) Rectangle");
            System.out.println("3) Circle");
            System.out.println("4) Quit");
            System.out.println();

            System.out.print("Choose a shape: ");

            int shape = keyboard.nextInt();
            System.out.println();

            // Check for user input
            if (shape == 1) {
                area_triangle(5, 6);

            } else if (shape == 2) {
                area_rectangle(4, 5);

            } else if (shape == 3) {
                area_circle(4);

            } else if (shape == 4) {
                quit();
                break;
            }
        }
    }

    public static double area_triangle(int base, int height) {

        Scanner keyboard = new Scanner(System.in);

        System.out.print("Base: ");
        base = keyboard.nextInt();

        System.out.print("Height: ");
        height = keyboard.nextInt();

        System.out.println();

        int A = (base * height) / 2;

        System.out.println("The area of a triangle is: " + A + ".");

        return A;
    }

    public static int area_rectangle(int length, int width) {

        Scanner keyboard = new Scanner(System.in);

        System.out.print("Length: ");
        length = keyboard.nextInt();

        System.out.print("Width: ");
        width = keyboard.nextInt();

        System.out.println();

        int A = length * width;

        System.out.println("The area of a rectangle is: " + A + ".");

        return A;
    }

    public static double area_circle(int radius) {

        Scanner keyboard = new Scanner(System.in);

        System.out.print("Radius: ");
        radius = keyboard.nextInt();

        System.out.println();

        double A = Math.PI * radius * radius;

        System.out.println("The area of a circle is: " + A + ".");

        return A;
    }

    public static String quit() {

        System.out.println("Quit program \n");

        return null;
    }
}