Finish challenge Happy Number

cediackermann/challenges/happyNumber/BUILD

@@ -0,0 +1,11 @@
+load("@rules_java//java:defs.bzl", "java_binary")
+
+package(default_visibility = ["//visibility:public"])
+
+java_binary(
+    name = "happyNumber",
+    main_class = "cediackermann.challenges.happyNumber.Main",
+    srcs = glob(["*.java"]),
+    deps = [
+    ],
+)

cediackermann/challenges/happyNumber/Main.java

@@ -0,0 +1,8 @@
+package cediackermann.challenges.happyNumber;
+
+public class Main {
+    public static void main(String[] args) {
+        Solution sol = new Solution();
+        System.out.println(sol.isHappy(2));
+    }
+}

cediackermann/challenges/happyNumber/Solution.java

@@ -0,0 +1,27 @@
+package cediackermann.challenges.happyNumber;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class Solution {
+    public boolean isHappy(int n) {
+        Set<Integer> seen = new HashSet<>();
+        
+        while (n != 1 && !seen.contains(n)) {
+            seen.add(n);
+            n = getNextGen(n);
+        }
+        
+        return n == 1;
+    }
+
+    private int getNextGen(int n) {
+        int nextGen = 0;
+        while (n > 0) {
+            int digit = n % 10;
+            nextGen += digit * digit;
+            n /= 10;
+        }
+        return nextGen;
+    }
+}