created classes and overrode methods doWork and stopWorks. Created Ma… by drpacci · Pull Request #2603 · mate-academy/jv-oop

drpacci · 2026-06-21T21:05:48Z

…chine's array and called those methods in the loop.

mateacademy-ai-mentor

Review Summary

Your solution is approved because all core requirements are implemented and functionally correct: Machine is abstract with doWork() and stopWork(), Truck, Bulldozer, and Excavator extend it and override both methods, and MainApp uses a Machine[] to call these methods polymorphically. The remaining issues are non-blocking: several messages have a typo (Buildozer instead of Bulldozer) and slightly awkward grammar (e.g., "Truck stop its work"), and there are redundant empty lines after class declarations and between methods, which conflict with [CHECKLIST ITEM #1] and [CHECKLIST ITEM #2]. These do not break functionality but you should still fix them: update all printed messages to use the correct machine names and clear past-tense English (for example, "Bulldozer started working" / "Bulldozer stopped working"), and remove extra blank lines immediately after class headers, between methods, and before closing braces. Also pay attention to the linter hints: add the missing space in MainApp.java line 5 (e.g., String[] args) and ensure there is a blank line before the first method in Machine.java as Checkstyle requires. Overall, the OOP structure and polymorphism are well done; polishing the messages and formatting will bring your code fully in line with the checklist and professional Java style.

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mateacademy-ai-mentor · 2026-06-21T21:07:14Z

+public class Bulldozer extends Machine {
+
+    public void doWork() {
+        System.out.println("Buildozer started its work");


This violates checklist item #2: messages should clearly and correctly indicate the machine type and what is happening. Here the type name is misspelled (Buildozer vs Bulldozer), and the wording/tense could be more precise (e.g., "Bulldozer started its work").

mateacademy-ai-mentor · 2026-06-21T21:07:14Z

+    }
+
+    public void stopWork() {
+        System.out.println("Buildozer stop its work");


This also violates checklist item #2 for the same reasons as above: the type name is inconsistent (Buildozer), and the message is not grammatically correct ("stop its work" vs "stopped its work").

mateacademy-ai-mentor · 2026-06-21T21:07:14Z

+public class Bulldozer extends Machine {
+


Checklist item #1 says "Please don't add redundant empty lines to your code. We don't need them after class declaration or method signature." The blank line between the class declaration and first method matches the bad example and should be removed.

mateacademy-ai-mentor · 2026-06-21T21:07:14Z

+    public void doWork() {
+        System.out.println("Buildozer started its work");
+    }
+


Checklist item #1 warns against redundant empty lines after method signatures; the empty line after this method declaration/body section falls into that pattern.

mateacademy-ai-mentor · 2026-06-21T21:07:14Z

+public class Bulldozer extends Machine {
+


Checklist item #1: there is a redundant empty line after the abstract class declaration; align with the improved example by keeping class and members directly together.

mateacademy-ai-mentor · 2026-06-21T21:07:14Z

+
+    public void doWork() {
+        System.out.println("Buildozer started its work");
+    }


Checklist item #1: this extra blank line between the abstract methods and the closing brace is unnecessary and matches the "Bad example" pattern.

mateacademy-ai-mentor · 2026-06-21T21:07:14Z

+public class Bulldozer extends Machine {
+
+    public void doWork() {
+        System.out.println("Buildozer started its work");


Checklist item #1: there is an extra empty line between the array initialization and the loop, similar to the bad example of redundant empty lines after code blocks.

mateacademy-ai-mentor · 2026-06-21T21:07:14Z

+public class Excavator extends Machine {
+
+    public void doWork() {
+        System.out.println("Excavator started its work");


The message misspells the class/type name (Buildozer instead of Bulldozer) and "started its work" is OK but could be made more natural (e.g., "Bulldozer started working") to better satisfy the "informative messages" checklist requirement.

mateacademy-ai-mentor · 2026-06-21T21:07:14Z

+    }
+
+    public void stopWork() {
+        System.out.println("Excavator stop its work");


Same typo (Buildozer) and the phrase "stop its work" is grammatically incorrect; consider "Bulldozer stopped its work" or "Bulldozer stopped working" to make the message clear and informative as required by the checklist.

mateacademy-ai-mentor · 2026-06-21T21:07:14Z

+public abstract class Machine {
+
+    public abstract void doWork();
+    public abstract void stopWork();


This violates checklist item: Write informative messages in methods. - Use English only and make messages informative - The message should indicate what type of Machine is working right now Truck, Bulldozer or Excavator. Here "Buildozer" is misspelled and the sentence is slightly ungrammatical; consider something like "Bulldozer started its work".

mateacademy-ai-mentor · 2026-06-21T21:07:19Z

+
+public abstract class Machine {
+
+    public abstract void doWork();


Although functionally correct, you can better follow the "use abstract references" checklist idea by instantiating via the interface but spacing the array more cleanly and consistently (e.g. Machine[] machines = { new Truck(), new Bulldozer(), new Excavator() };). The main point is already satisfied (using Machine as the type), so just keep this in mind stylistically.

mateacademy-ai-mentor · 2026-06-21T21:07:19Z

 public class MainApp {
+    public static void main(String[] args) {
+        Machine[] machines =  {new Truck(), new Bulldozer(), new Excavator()};



This violates checklist item about informative messages: the machine type is misspelled as Buildozer instead of Bulldozer, and the message should clearly and correctly indicate the machine type.

mateacademy-ai-mentor · 2026-06-21T21:07:19Z

+        for (Machine m : machines) {
+            m.doWork();
+            m.stopWork();
+        }


This also violates the informative message checklist: consider correcting the spelling (Bulldozer) and improving the phrasing to clearly say that the bulldozer has stopped working.

mateacademy-ai-mentor · 2026-06-21T21:07:19Z

+public class Truck extends Machine {
+
+    public void doWork() {
+        System.out.println("Truck started its work");


This message violates checklist item #2: "Write informative messages in methods". The machine type is misspelled (Buildozer instead of Bulldozer), so the message does not clearly and correctly indicate which machine is working.

mateacademy-ai-mentor · 2026-06-21T21:07:19Z

+    }
+
+    public void stopWork() {
+        System.out.println("Truck stop its work");


This also violates checklist item #2: the type name is misspelled (Buildozer), and the phrase "stop its work" is not clear or grammatically correct. Use a clear English sentence that states that the Bulldozer has stopped working.

mateacademy-ai-mentor · 2026-06-21T21:07:19Z

+public class Truck extends Machine {
+


This violates checklist item #1: "Please don't add redundant empty lines to your code. We don't need them after class declaration or method signature." The blank line after the class declaration is exactly the pattern shown in the bad example.

mateacademy-ai-mentor · 2026-06-21T21:07:19Z

+    public void doWork() {
+        System.out.println("Truck started its work");
+    }
+


This extra blank line between methods also matches the "Bad example" in checklist item #1 about redundant empty lines between method signatures and other code.

mateacademy-ai-mentor · 2026-06-21T21:07:19Z

+    }
+
+    public void stopWork() {
+        System.out.println("Truck stop its work");


Here the stopWork message uses "Truck stop its work", which is grammatically incorrect and less informative; per checklist item #2 you should use a clear English message that states the Truck has stopped working.

mateacademy-ai-mentor · 2026-06-21T21:07:19Z

+public class Truck extends Machine {
+


In this class too, the blank line right after class Truck extends Machine { matches the redundant empty-line pattern warned about in checklist item #1.

mateacademy-ai-mentor · 2026-06-21T21:07:19Z

+    public void doWork() {
+        System.out.println("Truck started its work");
+    }
+


This extra blank line between methods is another instance of the redundant empty lines that checklist item #1 asks you to avoid.

mateacademy-ai-mentor · 2026-06-21T21:07:23Z

+    }
+
+    public void stopWork() {
+        System.out.println("Truck stop its work");


The stopWork message uses "Excavator stop its work"; to comply with checklist item #2, rephrase to correct English that clearly indicates the Excavator has stopped working.

mateacademy-ai-mentor · 2026-06-21T21:07:23Z

+public class Truck extends Machine {
+


In Machine, the blank line right after the class declaration is the same pattern shown in the bad example for checklist item #1 (redundant empty line after class declaration).

mateacademy-ai-mentor · 2026-06-21T21:07:23Z

+
+    public void doWork() {
+        System.out.println("Truck started its work");
+    }


This extra blank line before the closing brace is another redundant empty line per checklist item #1.

mateacademy-ai-mentor · 2026-06-21T21:07:23Z

+public class Truck extends Machine {
+
+    public void doWork() {
+        System.out.println("Truck started its work");


In MainApp, the blank line between the array initialization and the for loop matches the redundant empty-line pattern that checklist item #1 tells you to avoid.

mateacademy-ai-mentor

Review Summary

Your solution is approved because all core functional requirements are correctly implemented: Machine is an abstract class with doWork() and stopWork(), Truck, Bulldozer, and Excavator extend it and override both methods, and MainApp uses a Machine[] and a loop to call these methods polymorphically. The printed messages are in clear English and explicitly mention each machine type, which satisfies the requirement for informative outputs. There are some remaining style issues with redundant empty lines (for example, extra blank lines in Excavator.java between the package and class declaration, before the for loop, and before the closing brace, and a similar extra blank line in Truck.java), but these are cosmetic and do not block functionality. You should still clean those up to align with the checklist item about avoiding redundant empty lines, but they do not prevent this solution from meeting the task’s main goals. Overall, the structure, inheritance, and polymorphic use of Machine and its subclasses are all implemented correctly—well done.

✨ Please rate this review in the Platform's notification center¹. I will be grateful for your feedback! ✨

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mateacademy-ai-mentor · 2026-06-21T22:45:53Z

@@ -0,0 +1,12 @@
+package core.basesyntax;
+


This violates checklist item Please don't add redundant empty lines to your code. We don't need them after class declaration or method signature. There is an extra blank line between the package and class declaration that should be removed.

mateacademy-ai-mentor · 2026-06-21T22:45:53Z

+public class Excavator extends Machine {
+    @Override
+    public void doWork() {
+        System.out.println("Excavator started its work");


This violates checklist item Please don't add redundant empty lines to your code. We don't need them after class declaration or method signature. Remove the extra blank line between the abstract methods and the closing brace.

mateacademy-ai-mentor · 2026-06-21T22:45:53Z

+public class Excavator extends Machine {
+    @Override
+    public void doWork() {
+        System.out.println("Excavator started its work");


This violates checklist item Please don't add redundant empty lines to your code. We don't need them after class declaration or method signature. The blank line before the for loop is redundant in this simple method and should be removed.

mateacademy-ai-mentor · 2026-06-21T22:45:53Z

@@ -0,0 +1,12 @@
+package core.basesyntax;
+


This violates checklist item Please don't add redundant empty lines to your code. We don't need them after class declaration or method signature. There is an extra blank line between the package and class declaration that should be removed.

mateacademy-ai-mentor · 2026-06-21T22:45:53Z

@@ -0,0 +1,12 @@
+package core.basesyntax;
+


This violates checklist item: Please don't add redundant empty lines to your code. We don't need them after class declaration or method signature. The blank line between the package and class declaration is considered redundant in this context.

created classes and overrode methods doWork and stopWorks. Created Ma…

55eca15

…chine's array and called those methods in the loop.

mateacademy-ai-mentor suggested changes Jun 21, 2026

View reviewed changes

mateacademy-ai-mentor reviewed Jun 21, 2026

View reviewed changes

drpacci added 4 commits June 21, 2026 23:08

Minor syntax fixes

f234a76

Fixed Buildozer to Bulldozer and @OverRide annotations added.

339c9b2

changed stop to stopped xD

80d39c0

extra lines were deleted

33dd700

drpacci requested a review from mateacademy-ai-mentor June 21, 2026 22:45

mateacademy-ai-mentor approved these changes Jun 21, 2026

View reviewed changes


		public abstract class Machine {

		public abstract void doWork();

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