title: Retained Heap size is more while using jackson ObjectMapper
body: <p>Am using Jackson mapper to convert my java objects to String, But these objects are not removed by GC in heap.</p>
  
  <p>My code </p>
  
  <pre><code>List&lt;Object[]&gt; reportList; // This contains my objects
  
  ObjectMapper map = new ObjectMapper(); // org.codehaus.jackson.map.ObjectMapper
  
  return map.writeValueAsString(reportList);
  </code></pre>
  
  <p>This returns String to my view layer, But Objects parsed via object mapper retained in heap. I have taken heap dump.</p>
  
  <pre><code>Class Name              |  Objects | Shallow Heap | Retained Heap
  ------------------------------------------------------------------
  char[]                  | 5,03,267 |  5,48,74,336 | &gt;= 54,874,336
  byte[]                  |   18,067 |  3,09,01,016 | &gt;= 30,901,016
  java.lang.reflect.Method| 2,60,262 |  2,08,20,960 | &gt;= 32,789,040
  java.util.HashMap$Entry | 4,31,423 |  1,38,05,536 | &gt;= 92,963,752
  java.lang.String        | 4,97,172 |  1,19,32,128 | &gt;= 60,889,416
  ------------------------------------------------------------------
  </code></pre>
  
  <p>While seeing char</p>
  
  <pre><code>Class Name                                                            | Shallow Heap | Retained Heap
  -----------------------------------------------------------------------------------------------------
  [2] char[4][] @ 0x72119e690                                           |           32 |      5,28,352
  '- _charBuffers org.codehaus.jackson.util.BufferRecycler @ 0x72119e658|           24 |      5,28,408
  -----------------------------------------------------------------------------------------------------
  Class Name                                                            | Shallow Heap | Retained Heap
  -----------------------------------------------------------------------------------------------------
  [2] char[4][] @ 0x721158a78                                           |           32 |      5,28,352
  '- _charBuffers org.codehaus.jackson.util.BufferRecycler @ 0x721158a40|           24 |      5,28,408
  -----------------------------------------------------------------------------------------------------
  Class Name                                                            | Shallow Heap | Retained Heap
  -----------------------------------------------------------------------------------------------------
  [2] char[4][] @ 0x7210bc5e0                                           |           32 |      5,28,352
  '- _charBuffers org.codehaus.jackson.util.BufferRecycler @ 0x7210bc5a8|           24 |      5,28,408
  -----------------------------------------------------------------------------------------------------
  </code></pre>
  
  <p>How to clean these objects from heap, is there any cleanup method exist.</p>