Java Project

[Smirre]

Hi everyone, I just registered with Java Forums and it looks fantastic. I just started studying java and I please need your help with a project I need to hand in.

The project I need to do is: (everything inside the quotation marks)...

"""Create a console calculator applicaion that:
* Takes one command line argument: your name and surname. When the
program starts, display the date and time with a welcome message for the
user.
* Display all the available options to the user. Your calculator must include
the arithmetic operations as well as at least five scientific operations of the
Math class.
-Your program must also have the ability to round a number and
truncate it.
-When you multiply by 2, you should not use the '*' operator to perform the
operation.
-Your program must also be able to reverse the sign of a number.
* Include sufficient error checking in your program to ensure that the user
only enters valid input. Make use of the String; Character, and other
wrapper classes to help you.
* Your program must be able to do conversions between decimal, octal and
hex numbers.
* Make use of a menu. You should give the user the option to end the
program when entering a certain option.
* When the program exits, display a message for the user, stating the
current time, and calculate and display how long the user used your
program.
* Make use of helper classes where possible.
* Use the SDK to run your program."""

I have already started to code this project, but I'm not sure if I am on the right track...

Here is my code so far...

import java.io.*;
import java.util.*;
import java.text.*;

public class Project {
	
	
	static String nameSurname = "";	
	static String num = null; 
	static String num2 = null; 
	static int checkNumber  = 0;
	static String choice = null;
	
	public static void main(String[] args) {
		
		SimpleDateFormat format1 = new SimpleDateFormat("EEEE, dd MMMM yyyy");
	    Date now = new Date();
	    
	    SimpleDateFormat format2 = new SimpleDateFormat("hh:m a");
	    Date now2 = new Date();
		
	    try {
	    	BufferedReader inStream = new BufferedReader (
                                      new InputStreamReader(System.in)
                                  );
	    	System.out.println("Please enter your name and surname :");
	    	nameSurname = inStream.readLine();
	    	System.out.println("\nA warm welcome to you " + nameSurname + " ,todays date is : " + format1.format(now));
	    	System.out.println("and the time is now exactly " + format2.format(now2) + ".");
	    	System.out.print("\nPlease enter a number and hit <ENTER>: ");
	    	num = inStream.readLine();
	    	checkNumber    = (int) Double.parseDouble(num);
	    	System.out.println("\nThe number you have entered is: " + num);
	    	System.out.print("\nPlease enter another number and hit <ENTER>: ");
	    	num2 = inStream.readLine();
	    	checkNumber    = (int) Double.parseDouble(num2);
	    	System.out.println("\nThe number you have entered is: " + num2);
	    	
	    } catch (NumberFormatException nfe) {
	    	System.out.println("You did not enter a valid number:  " + "\""+ num + "\"  is not a number!!");
	    	return;
	    } catch (IOException e) {
	    	System.out.println("IOException: " + e);
	    	return;
	    }		
	    
	    System.out.println("\nThe two numbers you entered was: " + num + " and " + num2);
	    System.out.println("Please select an option of what you would like to do with these numbers: ");
	    
	    System.out.println("\n*********************************************");
	    System.out.println("---------------------------------------------");
		System.out.println("Please select an option from the list below: ");
		System.out.println("---------------------------------------------");
		System.out.println("1 - Add");
		System.out.println("2 - Subtract");
		System.out.println("3 - Multiply");
		System.out.println("4 - Divide");
		System.out.println("5 - Maximum value of two numbers");
		System.out.println("6 - Minimum value of two numbers");
		System.out.println("7 - Absolute value of number");
		System.out.println("8 - Rounded number");
		System.out.println("9 - Exit");
		System.out.println("**********************************************");
		
		
		try {
	    	BufferedReader inStream2 = new BufferedReader (
                                      new InputStreamReader(System.in)
                                  );
	    	System.out.println("Please enter your option:");
	    	choice = inStream2.readLine();
	    	checkNumber    = (int) Integer.parseInt(choice);
	    	System.out.println("\nYou have entered choice number: " + choice);
	    } catch (NumberFormatException nfe) {
	    	System.out.println("You did not enter a valid  choice number:  " + "\""+ choice + "\"  is not on the list!!");
	    	return;
	    } catch (IOException e) {
	    	System.out.println("IOException: " + e);
	    	return;
	    }	
	}

}

Please have a look through my code and let me know where I have gone wrong.

Much appreciated.

Smirre

[Supamagier]

Please post the full error message you're getting, or the output it gives, and what it should give. Also... As a first year's Java student (I suppose you're that when you just started studying Java) you already gotta learn bitwise operations? Can't imagine.

[xcallmejudasx]

It runs fine. There are no compiler errors just logic errors.
After I enter my name and surname it asks me to enter a number. I have no idea what this number is or if it's just there to test number input? If I don't enter a number it displays "You did not enter a valid choice number...." but has no option to re-enter anything. You should fix it so it just returns to the Enter a number part instead of having to rerun the program.

Actually those 2 numbers you enter are used to calculate with. To make it more user friendly you might want to give the calculator options first and then have the user input the numbers.

You seem to be on the right track. Now you just need to create methods for each calculator option and then output the results. I'm guessing your going to keep track of how long they used the program by subtracting the time they "logged in" from the time they "log out" or do you have some sort of counter?

[Smirre]

Well here is the output it gives me so far,

Please enter your name and surname :
Johnny Bravo

A warm welcome to you Johnny Bravo ,todays date is : Thursday, 06 November 2008
and the time is now exactly 06:29 PM.

Please enter a number and hit <ENTER>: 87

The number you have entered is: 87

Please enter another number and hit <ENTER>: 69

The number you have entered is: 69

The two numbers you entered was: 87 and 69
Please select an option of what you would like to do with these numbers:

*********************************************
---------------------------------------------
Please select an option from the list below:
---------------------------------------------
1 - Add
2 - Subtract
3 - Multiply
4 - Divide
5 - Maximum value of two numbers
6 - Minimum value of two numbers
7 - Absolute value of number
8 - Rounded number
9 - Exit
**********************************************
Please enter your option:
1

You have entered choice number: 1

There are no error messages when I run the program, but the thing is I don't know what to do further when the user enters an option from the menu for e.g. '1'..

[Smirre]

xcalmejudasx, it makes alot of sense what you say but I'm not sure how do I go about so that the program returns to
the "enter a number part" instead of having to rerun the whole program??

[xcallmejudasx]

If you put your error checking and number entry put into seperate methods. Use a boolean value in your checking to say if the numbers are correct or not and call the specified method. If they aren't call the number entry method, if they are, call the "select an option" method and send those numbers in.

//Method check
	public void check(int num, int num2){
		//Do your error checking in here
		if(checking passes(pass = true)){
			optionsMethod();
		}
		else(pass = false){
			inputNumbers();
		}
	}

[Norm]

Where is the "enter the number" part? I searched for that string and didn't find it in your code.

Sounds like you need a loop with the "enter the number" part at the top of the loop.

[xcallmejudasx]

Where is the "enter the number" part? I searched for that string and didn't find it in your code.

Sounds like you need a loop with the "enter the number" part at the top of the loop.

System.out.print("\nPlease enter a number and hit <ENTER>: ");
	    	num = inStream.readLine();
	    	checkNumber    = (int) Double.parseDouble(num);
	    	System.out.println("\nThe number you have entered is: " + num);
	    	System.out.print("\nPlease enter another number and hit <ENTER>: ");
	    	num2 = inStream.readLine();
	    	checkNumber    = (int) Double.parseDouble(num2);
	    	System.out.println("\nThe number you have entered is: " + num2);

This is in his first try block.

I think breaking everything up into smaller methods and putting the try/catch blocks in those would make the program a little easier to follow and give you more control over everything since you can just *shivers* "goto" the section you want.

(memory)
ahh the joys of goto. realizing you forgot something and having to renumber hundreds of lines of code and then go and change every single goto state to accommodate the changes. man i love method calls
(/memory)