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POMust the .equals method for objects be overriden for instances of that object type in order for them to be used as keys in a HashMap
 

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  1. POMust the .equals method for objects be overriden for instances of that object type in order for them to be used as keys in a HashMap
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    <p>I am having trouble with Hashmaps. Currently, my HashMap is a HashMap of an enum called <code>Names</code>, using a key of <code>Key Signatures</code>, or <code>HashMap&lt;KeySignature, Names&gt;</code>. Currently, the Name Enum stores values of KeySignatures, or <code>C_FLAT_MAJOR(new KeySignature(7, Accidental.FLAT, Scale.MAJOR);</code>. To get the Enum version of a given KeySignature, I've created the HashMap explained above:</p> <pre><code>private static final HashMap&lt;KeySignature, Names&gt; lookup = new HashMap&lt;KeySignature, Names&gt;(); static { for (Names name : Names.values()){ lookup.put(new KeySignature(name.getKeySig()), name); } } </code></pre> <p>So, when I need to check what is the Enum version of a KeySignature, I call a method, located in the KeySignature class:</p> <pre><code>public Names getCommonName() { return Names.lookup.get(this); } </code></pre> <p>However, the value returned is always null.</p> <p>I cannot figure out what is causing this, but is seems as if the <code>HashMap.get()</code> method is comparing the key and the argument by reference rather than value. Do I have to override the .equals and .hash methods of KeySignature, or am I looking in the entirely wrong direction?</p>
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    1. USRussell
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    1. COYes you have to define manily `equals` in `KeySignature`
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      1. USsanbhat
 

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