Java Exercise 3

Objective:

• Methods in Java

Activity 1:

Write Java program that will ask the user to enter the width and length of a rectangle and then display the rectangle’s area. The program calls the following functions, which have not been written:

• getLength: This function should ask the user to enter the rectangle’s length and then return that value as a double .
• getWidth: This function should ask the user to enter the rectangle’s width and then return that value as a double .
• getArea: This function should accept the rectangle’s length and width as arguments and return the rectangle’s area. The area is calculated by multiplying the length by the width.
• displayData: This function should accept the rectangle’s area as argument and display it in an appropriate message on the screen.

Solution:

import java.util.Scanner;

public class Main {
    static double getLength() {
        double length;

        Scanner scanner = new Scanner(System.in);

        System.out.println("Enter Length of Rectangle: ");
        length = scanner.nextDouble();

        return length;
    }

    static double getWidth() {
        double width;

        Scanner scanner = new Scanner(System.in);

        System.out.println("Enter Width of Rectangle: ");
        width = scanner.nextDouble();

        return width;
    }

    static double getArea(double i, double j) {
        double area;
        area = i * j;

        return area;
    }

    static void displayData(double area) {
        System.out.println("Area of Rectangle is: " + area);
    }

    public static void main(String[] args) {
        double x, y, area;

        x = getLength();
        y = getWidth();

        area = getArea(x, y);
        displayData(area);
    }
}

Activity 2:

Write a function called displayShape that accepts size and shapetype as parameters and displays a square or a triangle of the required size.

So e.g. if the function is called with the following parameters:

displayShape(‘S’, 5); a square of size 5 is displayed as given

1	2	3	4	5
2	4	6	8	10
3	6	9	12	15
4	8	12	16	20
5	10	15	20	25

 

displayShape(‘T’, 6); a triangle of size 6 is displayed as given

                1

             1  1

           1  2  1

         1  3  3  1

       1  4  6  4  1

   1 5  10  10  5  1 

Solution:

import java.util.Scanner;

public class Main {
    static void printSquare(int size) {
        int num, res;
        for (int i = 1; i <= size; i++) {
            num = i;
            for (int j = 1; j <= size; j++) {
                res = num * j;
                System.out.print(res + "\t");
            }
            System.out.print("\n");
        }
        System.out.print("\n");
    }

    static void printTriangle(int size) {
        int coef = 1;
        for (int i = 0; i < size; i++) {
            for (int space = 1; space <= size - i; space++) {
                System.out.print("  ");
            }
            for (int j = 0; j <= i; j++) {
                if (j == 0 || i == 0) {
                    coef = 1;
                }
                else {
                    coef = coef * (i - j + 1) / j;
                }
                System.out.print(coef + "   ");
            }
            System.out.print("\n");
        }
    }

    public static void main(String[] args) {
        char choice2 = 'y';

        do {
            int size;
            char choice;

            Scanner scanner = new Scanner(System.in);

            System.out.println("Enter Size of Shape: ");
            size = scanner.nextInt();

            System.out.println("Enter s for Square-shape or t for triangle-shape: ");
            choice = scanner.next().charAt(0);

            if (choice == 's') {
                printSquare(size);
            }
            if (choice == 't') {
                printTriangle(size);
            }

            System.out.println("If you want to Repeat then press y. ");
            choice2 = scanner.next().charAt(0);

        } while (choice2 == 'y');

        scanner.close();
    }
}

Activity 3:

Write a program that converts a binary number into decimal number.

Solution:

import java.util.Scanner;

public class Main {
    static int decimalConverter(int num) {
        int dec = 0, i = 0, rem;
        boolean possible = true;
        while (num != 0) {
            rem = num % 10;
            num /= 10;
            if (rem == 0 || rem == 1) {
                dec += rem * (int)Math.pow(2, i);
                ++i;
            }
            else {
                System.out.println("Conversion not possible: it is not a binary number.");
                possible = false;
                break;
            }
        }
        if (possible) {
            return dec;
        }
        return 0;  // Need to return a value in all paths
    }

    public static void main(String[] args) {
        int n;

        Scanner scanner = new Scanner(System.in);

        System.out.print("Enter a Binary Number: ");
        n = scanner.nextInt();
        System.out.println("Decimal Number: " + decimalConverter(n));

        scanner.close();
    }
}