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POJava Hashmap two identical objects stored seperate
primarykey
Id
20302811
data
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20303556
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CommentCount
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CommunityOwnedDate
CreationDate
2013-11-30T16:43:21.353
FavoriteCount
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2013-11-30T17:45:40.647
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2013-11-30T17:40:32.160
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PostTypeId
1
Score
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text
Body
I overrided the hashCode and equals method of a class. I also wrote unit tests for it and it's all green. When I tested it out with a hashmap, I noticed something weird. I created 2 identical objects: <pre><code>obj1 = new PacmanVeld(field2); obj2 = new PacmanVeld(field2); </code></pre> I tested it out with this piece of code: <pre><code>Assert.assertTrue(obj1.hashCode() == obj2.hashCode()); //works Assert.assertTrue(obj1.equals(obj2)); //works HashMap<PacmanVeld, Integer> testMap = new HashMap<>(); testMap.put(obj1, 5); Assert.assertTrue(testMap.put(obj2, 7) == 5); //fails throws nullpointerexception Assert.assertTrue(testMap.get(obj1) == 7); //fails </code></pre> I don't understand why this won't work as I understand that in the algorithms of a HashMap, obj1 and obj2 are the same objects. The PacmanVeld class: <pre><code>public class PacmanVeld { private Node[][] nodes; public PacmanVeld(char[][] veld) { this.nodes = new Node[veld.length][veld[0].length]; for (int i = 0; i < veld.length; i++) { for (int j = 0; j < veld[i].length; j++) { switch (veld[i][j]) { case '%': nodes[i][j] = new Node(i, j, NodeType.WALL); break; case ' ': nodes[i][j] = new Node(i, j, NodeType.EMPTY); break; case '.': nodes[i][j] = new Node(i, j, NodeType.CRUMB); break; case 'P': nodes[i][j] = new Node(i, j, NodeType.PACMAN); break; } } } initFinish(); initPacman(); } //getters, setters & methods public boolean equals(PacmanVeld p) { if (p.nodes.length != nodes.length) { return false; } for (int i = 0; i < nodes.length; i++) { if (!Arrays.deepEquals(nodes[i], p.nodes[i])) { return false; } } return true; } @Override public int hashCode() { List<Node> nodeList = getNodeList(); return Arrays.deepHashCode(nodeList.toArray()); } private void initPacman() { for (Node[] rij : this.nodes) { for (Node n : rij) { if (n.isPacman()) { pacman = n; } } } } } </code></pre>
Tags
<java><junit><hashmap><hashcode>
Title
Java Hashmap two identical objects stored seperate
singulars
PostAcceptedAnswerId
1. PO
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1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. USwardva
UserOwnerUserId
1. USwardva
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PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
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1. This table or related slice is empty.
PostsParentIdCreationDate
1. PO
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2. PO
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3. PO
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1. VO
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 POJava Hashmap two identical objects stored seperate
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2. VO
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 POJava Hashmap two identical objects stored seperate
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