Methods in Machine class changed to public

src/main/java/core/basesyntax/MainApp.java

@@ -1,5 +1,54 @@
 package core.basesyntax;
 
-public class MainApp {
+abstract class Machine {
+    public abstract void doWork();
+    public abstract void stopWork();
+}
+
+class Truck extends Machine {
+    @Override
+    public void doWork() {
+        System.out.println("Truck has started working.");
+    }
+
+    @Override
+    public void stopWork() {
+        System.out.println("Truck has stopped working.");
+    }
+}
 
+class Bulldozer extends Machine {
+    @Override
+    public void doWork() {
+        System.out.println("Bulldozer has started working.");
+    }
+    @Override
+    public void stopWork() {
+        System.out.println("Bulldozer has stopped working.");
+    }
 }
+class Excavator extends Machine {
+    @Override
+    public void doWork() {
+        System.out.println("Excavator has started working.");
+    }
+    @Override
+    public void stopWork() {
+        System.out.println("Excavator has stopped working.");
+    }
+}
+
+public class MainApp {
+    public static void main(String[] args) {
+        Machine[] machines = {
+                new Truck(),
+                new Bulldozer(),
+                new Excavator()
+        };
+
+        for (Machine machine : machines) {
+            machine.doWork();
+            machine.stopWork();
+        }
+    }
+}