Update MainApp.java

src/main/java/core/basesyntax/Bulldozer.java

@@ -0,0 +1,12 @@
+package core.basesyntax;
+
+public class Bulldozer extends Machine {
+
+    public void doWork() {
+        System.out.println("Bulldozer started working");
+    }
+
+    public void stopWork() {
+        System.out.println("Bulldozer stoped working");
+    }
+}

src/main/java/core/basesyntax/Excavator.java

@@ -0,0 +1,12 @@
+package core.basesyntax;
+
+public class Excavator extends Machine {
+
+    public void doWork() {
+        System.out.println("Excavator started working");
+    }
+
+    public void stopWork() {
+        System.out.println("Excavator stoped working");
+    }
+}

src/main/java/core/basesyntax/Machine.java

@@ -0,0 +1,9 @@
+package core.basesyntax;
+
+public abstract class Machine {
+
+    public abstract void doWork();
+
+    public abstract void stopWork();
+
+}

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

@@ -1,5 +1,16 @@
 package core.basesyntax;
 
 public class MainApp {
-
+
+    public static void main(String[] args) {
+        Machine[] machines = new Machine[] {
+            new Truck(),
+            new Bulldozer(),
+            new Excavator()
+        };
+        for (Machine machine : machines) {
+            machine.doWork();
+            machine.stopWork();
+        }
+    }
 }

src/main/java/core/basesyntax/Truck.java

@@ -0,0 +1,12 @@
+package core.basesyntax;
+
+public class Truck extends Machine {
+
+    public void doWork() {
+        System.out.println("Truck started working");
+    }
+
+    public void stopWork() {
+        System.out.println("Truck stoped working");
+    }
+}