created classes, solved the task

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

@@ -0,0 +1,13 @@
+package core.basesyntax;
+
+public class Bulldozer extends Machine {
+    @Override
+    public void doWork() {
+        System.out.println("The buldozer started working");
+    }
+
+    @Override
+    public void stopWork() {
+        System.out.println("The buldozer stopped working");
+    }
+}

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

@@ -0,0 +1,13 @@
+package core.basesyntax;
+
+public class Excavator extends Machine {
+    @Override
+    public void doWork() {
+        System.out.println("The excavator started working");
+    }
+
+    @Override
+    public void stopWork() {
+        System.out.println("The excavator stopped working");
+    }
+}

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

@@ -0,0 +1,8 @@
+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 truck = new Truck();
+        Machine buldozer = new Bulldozer();
+        Machine excavator = new Excavator();
+
+        Machine [] machines = new Machine[] {truck, buldozer, excavator};
+        for (Machine machine : machines) {
+            machine.doWork();
+            machine.stopWork();
+        }
+    }
 
 }

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

@@ -0,0 +1,13 @@
+package core.basesyntax;
+
+public class Truck extends Machine {
+    @Override
+    public void doWork() {
+        System.out.println("The truck started working");
+    }
+
+    @Override
+    public void stopWork() {
+        System.out.println("The truck stopped working");
+    }
+}