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    <p>This is <em>not</em> a good idea. Map keys must be immutable to work properly, and yours are not.</p> <p>What are you really trying to do? When I see people doing things like this with data structures, it makes me think that they really need an object but have forgotten that Java's an object-oriented language.</p> <p>Looks like you want a crude dictionary to translate between languages. I'd create a <code>LanguageLookup</code> class that embedded those Maps and provide some methods to make it easier for users to interact with it. Better abstraction and encapsulation, more information hiding. Those should be your design objectives. Think about how to add other languages besides English and French so you can use it in other contexts. </p> <pre><code>public class LanguageLookup { private Map&lt;String, String&gt; dictionary; public LanguageLookup(Map&lt;String, String&gt; words) { this.dictionary = ((words == null) ? new HashMap&lt;String, String&gt;() : new HashMap&lt;String, String&gt;(words)); } public String lookup(String from) { return this.dictionary.get(from); } public boolean hasWord(String word) { return this.dictionary.containsKey(word); } } </code></pre> <p>In your case, it looks like you want to translate an English word to French and then see if the French dictionary contains that word:</p> <pre><code>Map&lt;String, String&gt; englishToFrenchWords = new HashMap&lt;String, String&gt;(); englishToFrenchWords.put("one", "une"); Map&lt;String, String&gt; frenchToEnglishWords = new HashMap&lt;String, String&gt;(); frenchToEnglishWords.put("une", "one"); LanguageLookup englishToFrench = new LanguageLookup(englishToFrenchWords); LanguageLookup frenchToEnglish = new LanguageLookup(frenchToEnglishWords); String french = englishToFrench.lookup("one"); boolean hasUne = frenchToEnglish.hasWord(french); </code></pre>
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    1. COI have thought about creating my own little 'keyClass' but it would have to either be a collection of them to link to a single item, or it would have to have a colection of key value pairs within it. So why re-create the wheel when java has collections that work, and then I just create my custom. I guess I could write my own TreeMap class, that inherits from treemap and then overide both hashCode() and compareTo() methods.
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    2. COThat's not a good enough reason to write your own TreeMap. If I were reviewing your code, I'd make you rip that out.
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    3. CO@duffmo I've added in a couple of edits in the hope of clarifying my situation. I'm coming around to using another better behaved DB (derby is going to be my choice, as I intend to use if again later for something else so I can use the same communication code) to convert my original legacy one into on a temp basis.
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