Check two if statements else run 3rd thing?

Question

Trying to find a solution to checking two different if conditions, and if neither are true output a third thing. Using a sample FizzBuzz code here to demonstrate the problem, when Fizz is for any multiple of 5 and Buzz for any multiple of 7. I wrote the "correct" way to do this first here.

//java
public class Fizzbuzz {
    public static void main(String[] args) {
        for(int i = 0; i < 100; i++ ) {
            if(i % 5 == 0 && i % 7 == 0) {
                System.out.println("FizzBuzz");
            } else if(i % 5 == 0) {
                System.out.println("Fizz");
            } else if(i % 7 == 0) {
                System.out.println("Buzz");
            } else {
                System.out.println(i);
            }
        }
    }
}

I thought this was bad because using 4 if statements to check for two possible things is theoretically a waste. It could easily be simplified to something like this:

//java
public class Fizzbuzz2 {
    public static void main(String[] args) {
        for(int i = 0; i < 100; i++ ) {
            if(i % 5 == 0) {
                System.out.print("Fizz");
            }
            if(i % 7 == 0) {
                System.out.print("Buzz");
            } 
            if(i % 5 != 0 && i % 7 != 0) {
                System.out.print(i);
            }
            System.out.print(\n);
        }
    }
}

Ideally, this could be simplified into something like this if (x), print fizz if (y), print buzz if neither of the first two, print i where printing fizz, buzz, and i don't add a newline, and print(/n) is at the end. Anyone have any idea how to do this (in any language?).

Answer 1

One way is to use the if statements to set a value, and then use switch / case to direct what happens based on the value.

For this example, I created a FizzBuzz type problem that test for multiples of 3, 5, and 7 for special handling. I tried to illustrate the flexibility of this approach by breaking the FizzBuzz pattern.

public static void fizzBuzzPop2 () {
        
  for (int i = 1; i < 350; ++i) {
    int flag = 0;
    if (i % 3 == 0) { flag += 1; }
    if (i % 5 == 0) { flag += 2; }
    if (i % 7 == 0) { flag += 4; }
    switch (flag) {
        case 0:                       // nothing special
            System.out.println (i);
            break;
        case 1:                      // multiple of 3
            System.out.println ("Fizz");
            break;
        case 2:                      // multiple of 5
            System.out.println ("Buzz");
            break;
        case 3:                      // multiple of 15 (3 and 5)
            System.out.println ("FizzBuzz");
            break;
        case 4:                     // multiple of 7
            System.out.println ("Pop");
            break;
        case 5:                     // multiple of 21 (3 and 7)
            System.out.println ("PopQuiz!");
            break;
        case 6:                     // multiple of 35 (5 and 7)
            System.out.println ("PopRocks");
            break;
        case 7:                    // multiple of 105 (3, 5, and 7)
            System.out.println ("A busy day");
            break;
       default:
           System.out.println ("****ERROR ERROR****");
           break;
    }
}

Each of 3 bits of flag represents the result of one Boolean test. Treating the results as a single number allows use of switch / case.

Answer 2

If you are trying to make fewer comparisons, you can use it:

for( int i = 0; i < 100; i ++ ) {
   String out = "";
   if( i % 5 == 0 ) {
      out = "Fizz";
   }
   if( i % 7 == 0 ) {
      out += "Buzz";
   }
   if( out.isEmpty() ) {
      out += i;
   }
   System.out.println( out );
}