Java Programming

I'm trying to make a program that can convert binary to decimal, decimal to binary, octal to hexadecimal, and hexadecimal to binary. It runs well, but I'm not getting the answers that I should be getting. I'll post the source code:

import java.io.*;
public class Compute {

public static void main (String[] args) {
int menu;
int num;
int rem;
String input;
String number;

BufferedReader dataIn = new BufferedReader (new InputStreamReader(System.in));

try{
System.out.println("Main Menu: \nPlease type the number of your choice: \n 1 - Binary to Decimal \n 2 - Decimal to Binary \n 3 - Octal to Hexadecimal \n 4 - Hexadecimal to Binary \n 5 - Quit");
input = dataIn.readLine();
menu = Integer.parseInt(input);

switch(menu){
case 1:
System.out.println("Enter a Binary Number: ");
number=dataIn.readLine();
num=Integer.parseInt(number);
num=num + 2;
rem=num/2;
System.out.println(rem);
break;
case 2:
System.out.println("Enter a Decimal Number: ");
number=dataIn.readLine();
num=Integer.parseInt(number);
while (num/2 != 0){
rem=num%2;
num=num/2;
if(num==0)
break;
System.out.println(num + " base 10 = " + rem + " base 2");
}
break;

case 3:
System.out.println("Enter an Octal Number: ");
number=dataIn.readLine();
num=Integer.parseInt(number);
num=num + 3;
rem=num/2;
System.out.println(rem);
break;

case 4:
System.out.println("Enter a Hexadecimal Number: ");
number=dataIn.readLine();
num=Integer.parseInt(number);
num=num * 2;
rem=num-2;
System.out.println(rem);
break;

case 5:
System.out.println("Good-bye!");
System.exit(0);

}

}
catch (IOException x){
System.out.println("Error In Input");

}
catch (NumberFormatException e){
System.out.println("Error In Input. Please Try Again.");
}

}
}

Ignore cases 1, 3, and 4; I haven't figured out what to do to convert one to the other.

Anyway, the only case that's really working is case 2. However, when I run it, I get this:

Enter a Decimal number:
10
5 base 10 = 0 base 2
2 base 10 = 1 base 2
1 base 10 = 0 base 2

My main problems:
1) The answer is wrong; it should be 110 base 2 instead of 010 base 2.
2) The output should be 10 base 10 = 110 base 2, not three separate lines per computation.
3) The program exits after I execute this part. I need it to return to the main menu.
4) Say I put 'A' in the "Main Menu" or "Enter A Decimal Number" part. It's an exception, but the program exits immediately. Is it possible for it to return to the main menu?

Help would be greatly appreciated. :) Also, I would appreciate it if someone can tell me what to do for the other cases.