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POStrange behavior while using HashSet
 

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  1. POStrange behavior while using HashSet
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    <p>I'm using a HashSet to store objects of a new type that I wrote. The type definition is of the following sort: </p> <pre><code>class Node{ Node arr[] = new Node[5]; boolean flag = false; } </code></pre> <p>I rewrote hashCode as follows:</p> <pre><code>int hash = Arrays.deepHashCode(arr); if(flag==true) return hash; else return -hash; </code></pre> <p>and equals:</p> <pre><code>public boolean equals(Object other){ Node t = (Node) other; return Arrays.deepEquals(arr, t.arr)&amp;&amp;(flag==t.flag); } </code></pre> <p>I'm adding words into the nodes (the nodes are trie nodes) and I'm doing so in dictionary order. I'm then storing the nodes into the hashset. The strange thing is that while the hashset works fine for words beginning with one letter, as soon as I get to words beginning with the next letter, my code gets stuck. For example, everything works fine for words beginning with 'a', but as soon as it gets to words beginning with 'b', it gets stuck. Same for 'c' and 'd' and so on.</p> <p>I narrowed it down to one line of code: the line where I'm adding the node to the hashset. </p> <p>Since I didn't write the hashset, I don't know what's going on here. I'm sure that that's where the code gets stuck (it doesn't crash. It seems to loop infinitely, but I'm not sure). Does anyone know what's going on?</p> <p>--Edit--</p> <p>Lots of head scratching and many print statements later, I have determined that the graph I was making was not actually a DAG, even though it should be and therefore, the deepHashCode and deepEquals functions were being thrown off. </p>
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    1. USefficiencyIsBliss
    1. USefficiencyIsBliss
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    1. COYou have to implement equals() as well. Can you post your equals code? You can find the code for HashSet in the JDK and step into it using your debugger (next to Run in your IDE).
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      1. POStrange behavior while using HashSet
      1. USPeter Lawrey
    2. COWhat do you mean by "stuck"? Does your code simply hang there (seemingly in an endless loop)? If so, check if you have a `Node` that references itself in `arr`. That would probably cause `deepHashCode()` to recurse endlessly.
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      1. POStrange behavior while using HashSet
      1. USJoachim Sauer
    3. CODid you implement the hashCode() function on Node?
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      1. USJustinKSU
 

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