implement MyHashMap functionality#1654
implement MyHashMap functionality#1654Sibertdom wants to merge 3 commits intomate-academy:masterfrom
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Review Summary
This requires a few changes. Your MyHashMap implementation is well-structured, but there's a critical issue that can cause a runtime error.
- The method for calculating the bucket index,
Math.abs(key.hashCode()), can return a negative number ifkey.hashCode()isInteger.MIN_VALUE. This will lead to anArrayIndexOutOfBoundsException. A safer way to ensure a non-negative index is to use a bitwise operation, like(key.hashCode() & 0x7fffffff) % table.length.
Additionally, please address these checklist violations:
- The number
2used for resizing is a magic number and should be a named constant. [CHECKLIST ITEM #2] - The constructor for the private inner
Nodeclass should not bepublic. [CHECKLIST ITEM #6]
Once you've addressed these points, your solution will be in great shape!
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Footnotes
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| private int getBucketIndex(K key) { | ||
| return (key == null) ? 0 : Math.abs(key.hashCode() % table.length); |
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Math.abs(key.hashCode()) can return a negative number if key.hashCode() is equal to Integer.MIN_VALUE. This would result in a negative array index, causing an ArrayIndexOutOfBoundsException. A safer approach to ensure a non-negative result is to use a bitwise operation, such as (key.hashCode() & 0x7fffffff) % table.length.
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| private void resize() { | ||
| Node<K, V>[] oldTable = table; | ||
| table = new Node[oldTable.length * 2]; |
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This violates checklist item #2: 'Any magic numbers should be constants'. The value 2 is a magic number. It's better to extract it into a named constant, like RESIZE_FACTOR, to improve code clarity and maintainability.
| private V value; | ||
| private Node<K, V> next; | ||
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| public Node(K key, V value, Node<K, V> next) { |
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This violates checklist item #6: 'If the method has only a utility purpose and is used only inside the same class, it should not be public'. The Node class is private to MyHashMap, so its constructor should not be public. Using a more restrictive access modifier like private or package-private would better encapsulate the implementation details.
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Review Summary
Excellent work on this iteration! I'm approving your solution as you have successfully addressed all the points from the previous review. You've fixed the critical hashCode bug, removed the magic number for resizing by creating a constant, and corrected the access modifier on the Node constructor. The code is now clean, robust, and fully meets all the project requirements. Keep up the great work!
✨ Please rate this review in the Platform's notification center1. I will be grateful for your feedback! ✨
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