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POGuava cache return an empty result on the second hit
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  1. POGuava cache return an empty result on the second hit
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    copied!<p>I have a strange (at least for me) behaviour with guava cache. After the first hit, the following accesses will return an empty object. I did not use strange evinction, so I can't figure out where I'm doing wrong. I declared the following LoadingCache:</p> <pre><code>LoadingCache&lt;String, Vector&lt;Location&gt;&gt; locations = CacheBuilder.newBuilder() .maximumSize(100000) .build( new CacheLoader&lt;String,Vector&lt;Location&gt;&gt;() { @Override public Vector&lt;Location&gt; load(String key) { return _getLocationListByTranscriptId(key); } }); </code></pre> <p>and I used it only in this method:</p> <pre><code>public Vector&lt;Location&gt; getLocationListByTranscriptId (String transcriptid) { if (transcriptid.equals("TCONS_00000046")) System.out.println("tcons found, will this work?"); Vector&lt;Location&gt; result; try { result = locations.get(transcriptid); } catch (ExecutionException e) { System.err.println("Error accessing cache, doing the hard way"); result = _getLocationListByTranscriptId(transcriptid); } if (transcriptid.equals("TCONS_00000046")){ if (result.size()==0){ System.out.println("this is a problem"); return null; } System.out.println("this is good!"); } return result; } </code></pre> <p>Iterating a Collection of input string, i get the following output:</p> <pre><code>tcons found, will this work? this is good! tcons found, will this work? this is a problem </code></pre> <p>So, the first time i use the cache, it works, but A) the value is not correctly stored for future accesses; B) the value is resetted for some strange behaviour. What can i do? Thanks all for reading this!</p> <p>EDIT: Thanks to axtavt answer I could immediately figure out where I was editing the resulting list. Don't know why, i was sure about guava cache returning a copy of the values. Thank you for the answer, and for the suggestions about defensive programming. (Sorry if i can't rate your answer yet).</p>
 

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