new

MainApp.java

@@ -0,0 +1,17 @@
+package core.basesyntax;
+
+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(); 
+            System.out.println("--------------------"); 
+        }
+    }
+}

MainApp1.java

@@ -0,0 +1,17 @@
+package core.basesyntax;
+
+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(); 
+            System.out.println("--------------------"); 
+        }
+    }
+}

public abstract class Machine {.java

@@ -0,0 +1,6 @@
+package core.basesyntax;
+
+public abstract class Machine {
+     public abstract void doWork();
+     public abstract void stopWork();
+}

public class Bulldozer extends Machine {.java

@@ -0,0 +1,14 @@
+package core.basesyntax;
+
+public class Bulldozer extends Machine {
+
+    @Override
+    public void doWork() {
+        System.out.println("Bulldozer started its work.");
+    }
+
+    @Override
+    public void stopWork() {
+        System.out.println("Bulldozer stopped working.");
+    }
+}

public class Excavator extends Machine {.java

@@ -0,0 +1,14 @@
+package core.basesyntax;
+
+public class Excavator extends Machine {
+
+    @Override
+    public void doWork() {
+        System.out.println("Excavator started its work.");
+    }
+
+    @Override
+    public void stopWork() {
+        System.out.println("Excavator stopped working.");
+    }
+}

public class Truck extends Machine {.java

@@ -0,0 +1,14 @@
+package core.basesyntax;
+
+public class Truck extends Machine {
+
+    @Override
+    public void doWork() {
+        System.out.println("Truck started its work.");
+    }
+
+    @Override
+    public void stopWork() {
+        System.out.println("Truck stopped working.");
+    }
+}