done #2413
done #2413
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Review Summary
Decision: REQUEST_CHANGES
You’ve implemented the class hierarchy and behavior well—Machine, Truck, Bulldozer, and Excavator all look correct and the loop over the machines works. However, there is a critical checklist violation in MainApp.java related to polymorphism that needs to be fixed before approval.
Critical issues to fix (blockers):
- Use abstract references instead of specific ones.
- Location:
src/main/java/core/basesyntax/MainApp.java - Likely lines near where variables are created (e.g., around the declarations for
truck,bulldozer,excavator). - Issue: Variables are declared with concrete types (
Truck,Bulldozer,Excavator) instead of the abstract typeMachine, violating the checklist requirement. - Why it’s wrong: The task explicitly requires programming to the abstraction to demonstrate polymorphism. Declaring them as
Machineensures your code relies on the abstract contract rather than concrete implementations. - How to fix: Change declarations to use the abstract type, for example:
Machine truck = new Truck();Machine bulldozer = new Bulldozer();Machine excavator = new Excavator();
- Also ensure any arrays or collections are of type
Machine[]or similar (you already iterate an array ofMachine, which is good).
- Location:
Minor notes (non-blocking):
- Everything else (messages, access modifiers, overrides) looks solid and clean.
Once you switch those variable declarations to Machine, you’ll fully meet the checklist and requirements. Nice work overall—this is a quick fix to align perfectly with polymorphism best practices.
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Important
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Footnotes
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| public class MainApp { | ||
| public static void main(String[] args) { | ||
| Truck truck = new Truck(); |
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This violates checklist item: "Use abstract references instead of specific ones." The variables truck, bulldozer, and excavator should be declared as Machine truck = new Truck();, etc., to fully utilize polymorphism and satisfy the requirements.
| public class MainApp { | ||
| public static void main(String[] args) { | ||
| Truck truck = new Truck(); | ||
| Bulldozer bulldozer = new Bulldozer(); |
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This violates checklist item: "Use abstract references instead of specific ones." The variables truck, bulldozer, and excavator should be declared as Machine bulldozer = new Bulldozer();, etc., to fully utilize polymorphism and satisfy the requirements.
| public static void main(String[] args) { | ||
| Truck truck = new Truck(); | ||
| Bulldozer bulldozer = new Bulldozer(); | ||
| Excavator excavator = new Excavator(); |
There was a problem hiding this comment.
This violates checklist item: "Use abstract references instead of specific ones." The variables truck, bulldozer, and excavator should be declared as Machine excavator = new Excavator();, etc., to fully utilize polymorphism and satisfy the requirements.
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Review Summary
Great work! Your implementation fully meets the task requirements and checklist:
- The abstract class
Machinecorrectly declarespublic abstract void doWork()andpublic abstract void stopWork(). Truck,Bulldozer, andExcavatorextendMachineand properly override both methods with clear, English messages identifying the machine type.- In
MainApp, you useMachinereferences, store them in aMachine[], and iterate to call both methods on each instance, demonstrating polymorphism as required. - Access modifiers are appropriate, and there are no redundant empty lines.
No critical issues found; functionality and requirements are fully satisfied. Nice job applying abstraction and polymorphism cleanly. Keep it up!
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Footnotes
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