Question

A Simple Calculator Summary: Write a console program (character based) to do simple calculations (addition, subtraction, multiplication and division) of two numbers, using your understanding of Java. Description: You need to write a program that will display a menu when it is run. The menu gives five choices of operation: addition, subtraction, multiplication, division, and a last choice to exit the program. It then prompts the user to make a choice of the calculation they want to do. Once the user selects the operation, it will check for valid menu choices (and give an appropriate message if a wrong choice was selected) and then prompts the user to enter two numbers, separated by a space. If the user enters valid numbers, it will do the operation desired, and then displays the result. If the user enters invalid numbers, it displays an error message and asks for the correct input. After displaying the result, it displays Press enter key to continue. Once enter key is pressed, it displays the menu again. The program repeats until the user selects the choice to exit.

Sample Run of the Program: Sample Run of the program:

Welcome to <John Doe’s> Handy Calculator.

1. Addition.

2. Subtraction.

3. Multiplication

4. Division

5. Exit.

What would you like to do? 3.

Please enter two floats to multiply, separated by a space: 24.0 4.0.

Result of multiplying 24.00 and 4.00 is 96.00.

Press enter key to continue ....   

Welcome to <John Doe’>s Handy Calculator.

1. Addition.

2. Subtraction.

3. Multiplication.

4. Division.

5. Exit.

What would you like to do? 4.

Please enter two floats to divide separated by a space: 2.0 0.

You can’t divide by zero please re-enter both floats: asasfs asdfasfas

You have entered invalid floats please re-enter: 16.0 4.0. Result of dividing 16.0 by 4.00 is 4.00.

Press enter key to continue ....

Welcome to <John Doe’>s Handy Calculator.

1. Addition.

2. Subtraction.

3. Multiplication

4. Division.

5. Exit.

What would you like to do? 5.

Thank you for using <John Doe’>s Handy Calculator.   

Note : 1) Replace the <John Doe’s> with your name. 2) Make sure to properly word the output for the choices and result. If user selects ‘1’ from the menu, the prompt should be for ‘Addition’ not multiplication as shown in the example. 3) 3, 24.0 4.0 are shown in the example to emphasize that it is entered by the user and not part of the program. Underline and italics are not a requirement. 4) Your program should allow input of integer and decimal numbers (floats). The output should always be in decimals, with two decimal digits as precision. 5) Make sure your program will continue displaying the menu after the result is shown and user has pressed the enter key. Your program will exit only when user selects 5. 6) If the user selects an option other than 1-5, show a message that they must select a number between 1 and 5. Give them a chance to re-enter. Continue until a valid number is entered.

7) If they enter invalid values instead of numbers (e.g. strings), provide an error message and give them chances to re-enter. Continue until valid numbers are entered. You don’t need to worry about range of floats. 8) Make sure to catch the divide by zero issue. In the case of a division choice, the second number should not be a zero. The users should be given a second chance to enter other than a zero. 9) You should decompose your program in many static methods. So, you can call these static methods from main method to do the functionality required. Your class need not to be instantiated with a ‘new’. All methods are directly called from main of same class becausethey are static methods

Answer 1

//Java Program for SImple Handy Calculator

import java.util.*;
import java.lang.*;
import java.text.DecimalFormat;//importing for decimal formats
class calculator
{
   static float input1,input2;
   public static void main(String[] args)
   {
       calculate(); //for calculations
   }
   public static void calculate()
   {
       Scanner input=new Scanner(System.in);
       int option=menu();//user choice input
       if(option>=1 && option<=5)
       {
           switch(option)
           {
               case 1:
                   add();//addition
                   break;
               case 2:
                   sub();//subtraction
                   break;
               case 3:
                   mul();//multiplication
                   break;
               case 4:
                   div();//division
                   break;
               case 5:
                   System.exit(0);//exit for the program
               default:
                   calculate();//if user prompts for wrong options

           }
       }
       else
       {
           System.out.println("You are supposed to Select Correct Options.");
           //used to show the Message to the User
           calculate();//to calculate again
       }
   }
   public static void add()
   {
       Scanner ai=new Scanner(System.in);//defining for taking inputs from console
       DecimalFormat df = new DecimalFormat(); //defining for decimal formats for 2 places
       df.setMaximumFractionDigits(2);
       System.out.println("Enter two values for Addition");
       try{
           input1=ai.nextFloat(); //first input from the user
           input2=ai.nextFloat(); //second input fro the user
           float result=input1+input2;
           System.out.print("Result of Adding "+input1+" and "+input2+" is :\t");
           System.out.println(df.format(result)); //printing result upto 2 deciaml places
           System.out.println("Press any key and press Enter");
           char temp=ai.next().charAt(0); //used for pressing enter
           if (temp!='~') {
               calculate();
           }
       }
       catch(Exception e)
       {
           System.out.println("You are Supposed to give input Correctly\n\n");
           //Messaging users to to give correct input
           calculate();
       }
      
   }
   public static void sub()
   {
       Scanner ai=new Scanner(System.in);//defining for taking inputs from console
       DecimalFormat df = new DecimalFormat();
       df.setMaximumFractionDigits(2);
       System.out.println("Enter two values for Subtraction");
       try{
           input1=ai.nextFloat();
           input2=ai.nextFloat();
           float result=input1-input2;
           System.out.print("Result of Subtracting "+input1+" and"+input2+" is :\t");
           System.out.println(df.format(result));
           System.out.println("Press any key and press Enter");
           char temp=ai.next().charAt(0);
           if (temp!='~') {
               calculate();
           }
       }
       catch(Exception e)
       {
           System.out.println("You are Supposed to give input Correctly\n\n");
           calculate();
       }
      
   }
   public static void mul()
   {
       Scanner ai=new Scanner(System.in);//defining for taking inputs from console
       DecimalFormat df = new DecimalFormat();
       df.setMaximumFractionDigits(2);
       System.out.println("Enter two values for Multiplication");
       try{
           input1=ai.nextFloat();
           input2=ai.nextFloat();
           float result=input1*input2;
           System.out.print("Result of Multiplying "+input1+" and "+input2+" is :\t");
           System.out.println(df.format(result));
           System.out.println("Press any key and press Enter");
           char temp=ai.next().charAt(0);
           if (temp!='~') {
               calculate();
           }
       }
       catch(Exception e)
       {
           System.out.println("You are Supposed to give input Correctly\n\n");
           calculate();
       }
      
   }
   public static void div()
   {
       Scanner ai=new Scanner(System.in);//defining for taking inputs from console
       DecimalFormat df = new DecimalFormat();
       df.setMaximumFractionDigits(2);
       System.out.println("Enter two values for Division");
       try{
           input1=ai.nextFloat();
           input2=ai.nextFloat();
           int temp1=(int)input2;
           while(temp1==0)
           {
               System.out.println("You cannot divide by zero.please re-enter");
               //to re take inputs from the user when Entered 0
               input2=ai.nextFloat();
               temp1=(int)input2;
           }
           float result=input1/input2;
           System.out.print("Result of Dividing "+input1+" by "+input2+" is :\t");
           System.out.println(df.format(result));
           System.out.println("Press any key and press Enter");
           char temp=ai.next().charAt(0);
           if (temp!='~') {
               calculate();
           }
       }
       catch(Exception e)
       {
           System.out.println("You are Supposed to give input Correctly\n\n");
           calculate();
       }
      
   }
   public static int menu()
   {
       Scanner mi=new Scanner(System.in);
       //here mi as menu_input
       System.out.println("Welcome to Adi's Handy Calculator\n");
       System.out.println("1.Addition\n2.Subtraction\n3.Multiplication\n4.Division\n5.Exit");
       System.out.print("What would you like to do?\t");
       int choice; //taking choice from user
       choice=mi.nextInt();
       return choice; //return user choice to calculate
   }
}

Note: I took Entered key as an Any character input to exit.