I am a beginner to Java and am learning about using methods. I want to make a simple calculator that uses methods effectively. I would like a review of my program, and I would also like to know if there is a better way or shortcuts to write this program better.
I would like to know at the same time about good coding style. Did I practice good coding style in my program? Where did I not practice good style? How could I improve this program so that it's in a good coding style?
import java.text.DecimalFormat;
import java.util.Scanner;
public class DoTheMath_A {
public static void main(String[] args) {
// First number storage
double num1 = getFirstNumber(); // Value - returning method.
// Second number storage
double num2 = getSecondNumber(); // Value - returning method.
// Displays Math Operations menu
showMenu(); // Void - returning method
// Math Operation choice storage
int choice = getSelection(); // Value - returning method
// Calculates the users numbers into an result. No output.
double result = doTheMath(choice, num1, num2); // Value - returning
// method
// Displays the output with formatting to show 2 decimal places.
displayResult(choice, result, num1, num2); // Void - returning method
} // end of main()
// Value - returning method =======================================
private static double getFirstNumber() {
Scanner input = new Scanner(System.in);
System.out.print("Enter the first number: ");
double num1 = input.nextDouble(); // First number storage
return num1; // Returns First number to main
} // end of getFirstNumber()
// Value - returning method =======================================
private static double getSecondNumber() {
Scanner input = new Scanner(System.in);
System.out.print("\nEnter the second number - "
+ "(Cannot be zero for Divison): ");
double num2 = input.nextDouble(); // Second number storage
return num2;
} // end of getSecondNumber()
// Void - returning method ============================
private static void showMenu() {
System.out.print("\n1. Addition\n2. Subtract\n3. Multiply"
+ "\n4. Divide\n\nWhich math operation? "
+ "Enter your choice: ");
} // end of showMenu()
// Value - returning method =======================================
private static int getSelection() {
Scanner input = new Scanner(System.in);
int choice = input.nextInt(); // Reads User pick for math operation and
// stores it into 'choice'
switch (choice) { // Start of Switch
case 1:
break;
case 2:
break;
case 3:
break;
case 4:
break;
default:
System.out.println("Illegal Operation");
} // end of Switch
return choice;
} // end of getSelection()
// Value - returning method =======================================
private static double doTheMath(int choice, double num1, double num2) {
double result;
if (choice == 1)
result = num1 + num2;
else if (choice == 2)
result = num1 - num2;
else if (choice == 3)
result = num1 * num2;
else
result = num1 / num2;
return result;
} // end of doTheMath(int choice, double num1, double num2)
// Void - returning method =======================================
private static void displayResult(int choice, double result, double num1, double num2) {
// formatting numbers to 1 decimal places
DecimalFormat df = new DecimalFormat("#,###,##0.0");
if (choice == 1)
System.out.println(num1 + " + " + num2 + " = " + df.format(result));
else if (choice == 2)
System.out.println(num1 + " - " + num2 + " = " + df.format(result));
else if (choice == 3)
System.out.println(num1 + " * " + num2 + " = " + df.format(result));
else
System.out.println(num1 + " / " + num2 + " = " + df.format(result));
} // end of displayResult(int choice, double result, double num1, double
// num2)
} // end of main()
/* Output ==========================
Enter the first number: 5
Enter the second number - (Cannot be zero for Divison): 2
1. Addition
2. Subtract
3. Multiply
4. Divide
Which math operation? Enter your choice: 4
5.0 / 2.0 = 2.5
*/
