Question

How can i write a while loop that checks to validate the first number is even and less than the second number. And if it isnt an error message is printed and the user is asked if two more integers are desired?

Answer 1

my code so far is:

import java.util.Scanner;

public class Calculate {



public static void main(String[] args) {

Scanner keyboard = new Scanner(System.in);

System.out.println("\tSum & Multiplication Calculator\n");

int num1, num2;

System.out.print("Enter two integers: ");
num1 = keyboard.nextInt();
num2 = keyboard.nextInt();

String input;
System.out.println("Enter a string: ");
input = keyboard.next();



if(input.equals("add"))
{
int sum;
sum = add(num1, num2);
System.out.print("The sum of two even numbers is: " + sum);

}
else if(input.equals("multiply"))
{
int product;
product = multiply(num1, num2);
System.out.print("The product of two integers is: " + product);
}
else
{
System.out.println("Error, invalid input!");
}

}
public static int add(int number1, int number2)
{
int sum = 0, index = 0;
for(index = number1; index <= number2; index++)
{
if(index%2==0)
{
sum+=index;
}
}
return sum;

}
public static int multiply(int number1, int number2)
{
int result;
result = number1 * number2;
return result;
}

}

Answer 2

@thomaster
how would i be able to do write one/

Answer 3

@e.mccormick
how would i be able to write one?

Answer 4

When people copy code from here, it can collapse all onto one line, making it hard to work with. For short code, putting ``` above and below the block stops this.

For longer code blocks, code pasting sites are great:
http://dpaste.com
http://pastebin.com
https://gist.github.com/
http://pastie.org
http://codepad.org
http://ideone.com
http://www.repl.it/

Answer 5

ok i'll do that first then...be back in a min

Answer 6

http://dpaste.com/1393103/ this is my code

Answer 7

Kk. Thanks. Makes it easier to try things. I like dpaste for quick stuff I intend to have go away soon. Pastebin is very nice for stuff that lasts longer. And many people love others.

Answer 8

i didn't know these kind of websites existed

Answer 9

Neither did I till I came here!

A while or do while loop is geneally best for mandetory input.

Answer 10

the whole code besides the static methods will be in a do-while loop..the do-while loop is supposed to repeat the whole program if a yes or Yes is entered

the while loop is supposed to be used for input validation if "add" is indicated....i've tried but the while loop i was attempting had syntax errors or infinite loops

Answer 11

```
boolean verify = true;
while(verify){
get some input
if correct verify = false
else error mesage/re-prompt
}
```

Answer 12

ok and verify is the boolean expression itself

Answer 13

Well, it is a variable. You are just using true and false because those are how loops are exited. While it is true, it loops. So you set it to false to exit the loop cleanly.

Answer 14

See, it is best to clean up input before it is passed to the other function. Or you need to use excepton handling in that function.