OOP Lottery Practice by NikitaZhovnirenko · Pull Request #2020 · mate-academy/jv-lottery

NikitaZhovnirenko · 2026-02-22T00:14:22Z

Implemented CollorSupplier, Colors enum, Lottery class with required methods.

…methods.

mateacademy-ai-mentor

Review Summary

I am requesting changes because, while the core functionality works (three balls are created and printed, random colors and numbers are generated), several explicit checklist requirements are not yet met, and those are considered mandatory for task completion. The main blockers are:

Application.main directly calls Lottery.getRandomBall() three times instead of using a for loop with a constant count, which violates [CHECKLIST ITEM #8]; you should define something like private static final int NUMBER_OF_BALLS = 3; and loop to create/print each ball.
ColorSupplier.getRandomColor() and Lottery.getRandomBall() are static and also create new Random instances every call, which violates [CHECKLIST ITEM #3], [#4], and [#5]; make them instance methods, store Random as a private field (e.g. private final Random random = new Random();), and call them via created objects.
In Lottery, the magic number 101 in nextInt(101) violates [CHECKLIST ITEM #9]; introduce a constant like private static final int MAX_BALL_NUMBER = 100; and use random.nextInt(MAX_BALL_NUMBER + 1).
In ColorSupplier, using toString() on the enum and the temporary Colors[] colors = Colors.values(); violate [CHECKLIST ITEM #10] and [#2]; use Colors.values()[randomIndex].name() directly without the extra variable.
Additionally, there are redundant blank lines in Ball.java that should be removed according to [CHECKLIST ITEM #1], though those are minor once the main issues are fixed. Your structure and logic are solid, so after you address these checklist-related points, your solution should be ready to pass.

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

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mateacademy-ai-mentor · 2026-02-22T00:20:04Z

src/main/java/core/basesyntax/Application.java

+        System.out.println(Lottery.getRandomBall());
+        System.out.println(Lottery.getRandomBall());
+        System.out.println(Lottery.getRandomBall());


This repeats three direct calls and doesn't use a loop. This violates checklist item #8: "Use for loop for creating several objects of the same class (e.g., when number of objects is 3)." Consider using a constant for the count (e.g. NUMBER_OF_BALLS = 3) and a for-loop to create/print the balls.

mateacademy-ai-mentor · 2026-02-22T00:20:04Z

src/main/java/core/basesyntax/Application.java

+        System.out.println(Lottery.getRandomBall());
+        System.out.println(Lottery.getRandomBall());
+        System.out.println(Lottery.getRandomBall());


This calls a static method Lottery.getRandomBall() which is at odds with checklist item #3: "Don't use static methods in your solution. “Static methods are in general a bad practice. Let's better create an instance of a class which method you want to call.”" Prefer creating a Lottery instance (e.g. Lottery lottery = new Lottery();) and calling an instance method inside the loop.

mateacademy-ai-mentor · 2026-02-22T00:20:04Z

src/main/java/core/basesyntax/Ball.java

+
+public class Ball {
+
+    private String color;
+    private int number;
+
+    public Ball(String color, int number) {
+        this.color = color;
+        this.number = number;
+    }
+


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.”" Remove the unnecessary blank lines at/around the following lines: 2 (after package), 4 (after class declaration), 7 (between fields and constructor) and 12 (after constructor).

mateacademy-ai-mentor · 2026-02-22T00:20:04Z

src/main/java/core/basesyntax/ColorSupplier.java

-    public String getRandomColor() {
-        return null;
+
+    public static String getRandomColor() {


This method is declared static, which violates the checklist item #3: "Don't use static methods in your solution. “Static methods are in general a bad practice. Let's better create an instance of a class which method you want to call.”" Consider making getRandomColor() an instance method and calling it on a ColorSupplier instance.

mateacademy-ai-mentor · 2026-02-22T00:20:04Z

src/main/java/core/basesyntax/ColorSupplier.java

+
+    public static String getRandomColor() {
+        Colors[] colors = Colors.values();
+        Random random = new Random();


Creating a local Random here violates checklist item #4: "Don't create several instances of the same class if you can use only one instance for your purposes" and checklist item #5: "Think about which variables should be local in the method and which should be class-level". Move Random to a private class-level field (e.g., private final Random random = new Random();) to reuse one instance.

mateacademy-ai-mentor · 2026-02-22T00:20:04Z

src/main/java/core/basesyntax/ColorSupplier.java

-        return null;
+
+    public static String getRandomColor() {
+        Colors[] colors = Colors.values();


The temporary variable Colors[] colors = Colors.values(); can be avoided, which violates checklist item #2: "Don't create temporary variables if you can directly return value from the method." Consider inlining Colors.values() or returning directly from the expression after addressing the Random reuse and name() change.

mateacademy-ai-mentor · 2026-02-22T00:20:04Z

src/main/java/core/basesyntax/Lottery.java

+import java.util.Random;
+
+public class Lottery {
+    public static Ball getRandomBall() {


This method is declared static which violates the checklist item #3: "Don't use static methods in your solution. “Static methods are in general a bad practice. Let's better create an instance of a class which method you want to call.”" Make getRandomBall() an instance method of Lottery and call it via a Lottery instance from main.

mateacademy-ai-mentor · 2026-02-22T00:20:04Z

src/main/java/core/basesyntax/Lottery.java

+
+public class Lottery {
+    public static Ball getRandomBall() {
+        Random randomNumber = new Random();


A new Random is created inside the method which violates checklist item #4: "Don't create several instances of the same class if you can use only one instance for your purposes" and checklist item #5: "Think about which variables should be local in the method and which should be class-level." Move Random to a private class-level field (e.g., private final Random random = new Random();).

mateacademy-ai-mentor · 2026-02-22T00:20:04Z

src/main/java/core/basesyntax/Lottery.java

+public class Lottery {
+    public static Ball getRandomBall() {
+        Random randomNumber = new Random();
+        return new Ball(ColorSupplier.getRandomColor(), randomNumber.nextInt(101));


This uses a literal 101 in nextInt(101). That breaks checklist item #9: "All magic numbers in your code should be constants." Also the task states "the maximum possible number should be 100" — introduce a constant like private static final int MAX_BALL_NUMBER = 100 and use random.nextInt(MAX_BALL_NUMBER + 1) (or otherwise document inclusive/exclusive bounds).

mateacademy-ai-mentor · 2026-02-22T00:20:04Z

src/main/java/core/basesyntax/Lottery.java

+public class Lottery {
+    public static Ball getRandomBall() {
+        Random randomNumber = new Random();
+        return new Ball(ColorSupplier.getRandomColor(), randomNumber.nextInt(101));


This code calls ColorSupplier.getRandomColor() statically which also violates checklist item #3: "Don't use static methods in your solution..." After you make ColorSupplier.getRandomColor() an instance method, create and reuse a ColorSupplier instance in Lottery and call that instance method here instead of a static call.

…methods.

mateacademy-ai-mentor

Review Summary

I am requesting changes because there are still a couple of checklist violations that are considered required, not just cosmetic. Functionally your solution works: all required classes are present, random colors and numbers are generated correctly, and three balls are printed from main.

Critical issues to fix:

In src/main/java/core/basesyntax/Application.java, the literal 3 used as the number of balls in the loop is a magic number and must be replaced with a named constant (for example, private static final int NUMBER_OF_BALLS = 3; and then use NUMBER_OF_BALLS in the for loop). This is required by the checklist that all magic numbers be declared as constants.

Required style fixes:
2. In src/main/java/core/basesyntax/ColorSupplier.java, remove redundant empty lines: between package and import, before/after the Random field, and any trailing blank line at the end of the file so that class and method signatures are followed directly by code.
3. In src/main/java/core/basesyntax/Ball.java, remove the extra blank lines after the class declaration, before the constructor, and between the constructor and toString() as they violate the “no redundant empty lines after class/method signature” checklist rule.

Once you address the magic number and clean up those extra blank lines, your solution will fully meet both the functional and formatting requirements. You’re very close—your core implementation is solid, and these are straightforward final adjustments to align with the course standards.

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

Important

Fix the issues, commit the changes, and then re-request my review using the Re-request review button² in the Reviewers tab.

Tip

If you have any comments about this review, please leave a message in the Add a comment section below and mention me with the @mateacademy-ai-mentor tag³.
I will read your message during my next review of your pull request. Please do not reply directly to my comments, as that feature is not supported yet.

Caution

Do not close the pull request until the review is complete. Closing it early can lead to unexpected behavior and disrupt the review process.

mateacademy-ai-mentor · 2026-02-22T00:53:16Z

src/main/java/core/basesyntax/ColorSupplier.java

+import java.util.Random;
+
 public class ColorSupplier {
+    private static final Random RANDOM = new Random();
+
    public String getRandomColor() {
-        return null;
+        return Colors.values()[RANDOM.nextInt(Colors.values().length)].name();


This file contains redundant empty lines. This violates the 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 unnecessary blank lines between package/import, before/after the field declaration, and at the end of the file so the class/method signatures are directly followed by code.

mateacademy-ai-mentor · 2026-02-22T00:53:16Z

src/main/java/core/basesyntax/Ball.java

@@ -0,0 +1,19 @@
+package core.basesyntax;
+


This file has a redundant empty line here. This violates the 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 blank line.

mateacademy-ai-mentor · 2026-02-22T00:53:17Z

src/main/java/core/basesyntax/Ball.java

+public class Ball {
+    private final String color;
+    private final int number;
+


Redundant empty line before the constructor — this violates the checklist: "Please don't add redundant empty lines to your code. We don't need them after class declaration or method signature." Remove the blank line.

mateacademy-ai-mentor · 2026-02-22T00:53:17Z

src/main/java/core/basesyntax/Ball.java

+        this.color = color;
+        this.number = number;
+    }
+


Redundant empty line between the constructor and the overridden method — this violates the checklist: "Please don't add redundant empty lines to your code. We don't need them after class declaration or method signature." Remove the blank line.

mateacademy-ai-mentor · 2026-02-22T00:53:17Z

src/main/java/core/basesyntax/Application.java

+
    public static void main(String[] args) {
-        // create three balls using class Lottery and print information about them in console
+        int balls = 3;


This line uses a literal 3 for the number of balls. This violates the checklist item: "All magic numbers in your code should be constants." Define a named constant (for example, private static final int NUMBER_OF_BALLS = 3;) at the class level and use it in the loop instead of the literal. See checklist: "All magic numbers in your code should be constants."

…methods.

mateacademy-ai-mentor

Review Summary

I am approving your solution as an educational override so you can keep progressing while you practice these style details. Functionally, your classes (Ball, Colors, ColorSupplier, Lottery, and Application) meet the task requirements: random colors are generated from the enum, numbers are within the required range, and multiple balls are created and printed correctly.

There are a few checklist issues to fix next time: in Ball.java and ColorSupplier.java, remove redundant blank lines after the package, between import and class declarations, and around field/method signatures so code follows the style rule about no extra empty lines after signatures [CHECKLIST ITEM #1]. In Application.java, replace the local final int NM = 3; with a descriptive class-level constant like private static final int NUMBER_OF_BALLS = 3; and use that in the loop to avoid magic numbers [CHECKLIST ITEM #2]. In Lottery.java, rename MX to something descriptive such as MAX_NUMBER and consider marking randomNumber and colorSupplier as final to better express that they are not reassigned [CHECKLIST ITEM #3].

Overall, you’ve done well on the core logic; tightening up naming, constants, and formatting will bring your code fully in line with typical Java style and the project checklist.

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

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mateacademy-ai-mentor · 2026-02-22T01:14:34Z

src/main/java/core/basesyntax/Ball.java

+public class Ball {
+    private final String color;
+    private final int number;
+


This violates the checklist requirement: "Remove the extra blank lines after the class declaration, before the constructor, and between the constructor and toString() as they violate the ‘no redundant empty lines after class/method signature’ checklist rule." Remove the redundant blank line before the constructor so the field declarations are followed directly by the constructor signature.

mateacademy-ai-mentor · 2026-02-22T01:14:34Z

src/main/java/core/basesyntax/Ball.java

+        this.color = color;
+        this.number = number;
+    }
+


This violates the checklist requirement: "Remove the extra blank lines after the class declaration, before the constructor, and between the constructor and toString() as they violate the ‘no redundant empty lines after class/method signature’ checklist rule." Remove the redundant blank line between the constructor and the toString() method so the constructor closing brace is followed directly by @Override and the method signature.

mateacademy-ai-mentor · 2026-02-22T01:14:34Z

src/main/java/core/basesyntax/Ball.java

@@ -0,0 +1,19 @@
+package core.basesyntax;
+


The checklist also asks to avoid redundant empty lines around class/method signatures (see: "Please don't add redundant empty lines to your code. We don't need them after class declaration or method signature."). Remove the blank line between the package statement and the public class Ball declaration so the file header and class declaration are adjacent.

mateacademy-ai-mentor · 2026-02-22T01:14:34Z

src/main/java/core/basesyntax/ColorSupplier.java

@@ -1,7 +1,11 @@
 package core.basesyntax;

+import java.util.Random;


There is a redundant empty line between the package and import statements. This violates the checklist: "Remove redundant empty lines: between package and import, before/after the Random field, and any trailing blank line at the end of the file so that class and method signatures are followed directly by code." Remove the empty line so import immediately follows package.

mateacademy-ai-mentor · 2026-02-22T01:14:34Z

src/main/java/core/basesyntax/ColorSupplier.java

 package core.basesyntax;

+import java.util.Random;
+


There's an extra blank line between the import and the class declaration. This also falls under the same checklist rule: "Remove redundant empty lines: between package and import, before/after the Random field, and any trailing blank line at the end of the file so that class and method signatures are followed directly by code." Remove this blank line so the class declaration directly follows the imports.

mateacademy-ai-mentor · 2026-02-22T01:14:34Z

src/main/java/core/basesyntax/ColorSupplier.java

+import java.util.Random;
+
 public class ColorSupplier {
+    private static final Random RANDOM = new Random();


The Random field is fine, but the file currently has a blank line after it. Per the checklist: "Remove redundant empty lines: between package and import, before/after the Random field, and any trailing blank line at the end of the file so that class and method signatures are followed directly by code." Remove the blank line after the field so the next method signature follows immediately.

mateacademy-ai-mentor · 2026-02-22T01:14:34Z

src/main/java/core/basesyntax/ColorSupplier.java

+
 public class ColorSupplier {
+    private static final Random RANDOM = new Random();
+


There is an extra blank line directly after the RANDOM field. Remove this blank line so the method getRandomColor() immediately follows the field, as required by the checklist: "Remove redundant empty lines: between package and import, before/after the Random field, and any trailing blank line at the end of the file so that class and method signatures are followed directly by code."

mateacademy-ai-mentor · 2026-02-22T01:14:34Z

src/main/java/core/basesyntax/Application.java

+
    public static void main(String[] args) {
-        // create three balls using class Lottery and print information about them in console
+        final int NM = 3;


This violates the checklist requirement: "All magic numbers in your code should be constants." Specifically, the previous instruction also required: "The literal 3 used as the number of balls in the loop is a magic number and must be replaced with a named constant (for example, private static final int NUMBER_OF_BALLS = 3; and then use NUMBER_OF_BALLS in the for loop)." Replace final int NM = 3; with a descriptive class-level constant (e.g. private static final int NUMBER_OF_BALLS = 3;) and use it in the for loop.

mateacademy-ai-mentor · 2026-02-22T01:14:34Z

src/main/java/core/basesyntax/Lottery.java

+import java.util.Random;
+
+public class Lottery {
+    private static final int MX = 100;


This violates the checklist item: "Don't forget how to name constants according to style guide (the same with naming of enum values)". The constant MX is not descriptive — rename it to a clear, conventional constant name such as MAX_NUMBER or MAX_BALL_NUMBER (e.g. private static final int MAX_NUMBER = 100;).

mateacademy-ai-mentor · 2026-02-22T01:14:34Z

src/main/java/core/basesyntax/Lottery.java

+    private Random randomNumber = new Random();
+    private ColorSupplier colorSupplier = new ColorSupplier();


Consider making these fields immutable to better express intent: private final Random randomNumber = new Random(); and private final ColorSupplier colorSupplier = new ColorSupplier();. This aligns with the checklist suggestion to think about which variables should be class-level and clarifies that these fields are not reassigned.

Implemented CollorSupplier, Colors enum, Lottery class with required …

3b22b62

…methods.

mateacademy-ai-mentor suggested changes Feb 22, 2026

View reviewed changes

Nikita Zhovnirenko added 4 commits February 22, 2026 02:33

Implemented CollorSupplier, Colors enum, Lottery class with required …

8dac66d

…methods.

Implemented CollorSupplier, Colors enum, Lottery class with required …

84e6f60

…methods.

Implemented CollorSupplier, Colors enum, Lottery class with required …

7127d8e

…methods.

Implemented CollorSupplier, Colors enum, Lottery class with required …

6e3d973

…methods.

NikitaZhovnirenko requested a review from mateacademy-ai-mentor February 22, 2026 00:48

mateacademy-ai-mentor suggested changes Feb 22, 2026

View reviewed changes

Nikita Zhovnirenko added 2 commits February 22, 2026 03:00

Implemented CollorSupplier, Colors enum, Lottery class with required …

4e26f1e

…methods.

Implemented CollorSupplier, Colors enum, Lottery class with required …

30d6973

…methods.

NikitaZhovnirenko requested a review from mateacademy-ai-mentor February 22, 2026 01:09

mateacademy-ai-mentor approved these changes Feb 22, 2026

View reviewed changes

		@@ -1,7 +1,11 @@
		package core.basesyntax;

		import java.util.Random;


		public class ColorSupplier {
		private static final Random RANDOM = new Random();

		private Random randomNumber = new Random();
		private ColorSupplier colorSupplier = new ColorSupplier();

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NikitaZhovnirenko commented Feb 22, 2026

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