Groovy Category Example

I cut my Java teeth on an old edition of Java Examples in a Nutshell. I thought it might be a good exercise to translate some of the Java code to Groovy. By the second example in the book I realized I was right. The example prints out every number from 1 to 100, except that if the number the number is divisible by 5 it prints “fizz,” if it is divisible by 7 it prints “buzz,” and if it is divisible by both 5 and 7 it prints “fizzbuzz.”

Like most examples in the book, the Java code is not exactly exemplary, as evidenced here:

public class FizzBuzz {          public static void main(String[] args) {         for (int i = 1; i <= 100; i++) {             if (((i % 5) == 0) && ((i % 7) == 0))                 System.out.print("fizzbuzz");             else if ((i % 5) == 0)                 System.out.print("fizz");             else if ((i % 7) == 0)                 System.out.print("buzz");             else                 System.out.print(i);         } System.out.print(" ");     } }

I like self-documenting code so rather than use comments to explain the logic, I try to write code that is readable by non-programmers. Using a Groovy Category to add a method to an existing Java class makes that job easier. Since the Category examples on the Groovy site are not very intuitive, I thought I’d share an example here:

use (Multiplicity.class) {   range = 1..100   range.each {number ->     if (number.isMultipleOf(5) && number.isMultipleOf(7)) {       print "fizzbuzz"     } else if (number.isMultipleOf(5)) {       print "fizz"     } else if (number.isMultipleOf(7)) {       print "buzz"     } else {       print "${number}"     }     print " "   } }    class Multiplicity {   static boolean isMultipleOf(Integer dividend, Integer divisor) {     dividend % divisor == 0   } }

This is what I like about Groovy. Not only is there less code (fewer keystrokes) but (and maybe more importantly) there is less to read in order to grasp the logic.