Main is in SolverMain.java

app/src/main/java/sudoku/App.java

@@ -1,14 +0,0 @@
-/*
- * This Java source file was generated by the Gradle 'init' task.
- */
-package sudoku;
-
-public class App {
-    public String getGreeting() {
-        return "Hello World!";
-    }
-
-    public static void main(String[] args) {
-        System.out.println(new App().getGreeting());
-    }
-}

app/src/main/java/sudoku/SolverMain.java

@@ -0,0 +1,7 @@
+package sudoku;
+
+public class SolverMain {
+    public static void main(String[] args) {
+        System.out.println("Hello world!");
+    }
+}