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  1. JDK
  2. JDK-6676058

ClassCastException leaks memory on Java 6 (win)

    Details

    • Subcomponent:
    • CPU:
      x86
    • OS:
      windows_xp

      Description

      FULL PRODUCT VERSION :
      java version "1.6.0_04"
      Java(TM) SE Runtime Environment (build 1.6.0_04-b12)
      Java HotSpot(TM) Client VM (build 10.0-b19, mixed mode, sharing)

      ADDITIONAL OS VERSION INFORMATION :
      Windows XP Professional Service Pack 2

      A DESCRIPTION OF THE PROBLEM :
      Attempting to cast a nonNumber object to Number results in a ClassCastException, which results in a sizeable memory leak if there is a high frequency of such exceptions,

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Compile and run the attached test program and monitor the Memory Usage using the Task Manager or Process Explorer. It will grow considerably using Java 6 (any release) or Java 7, but not with Java 5.


      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      Both the Java heap and the overall memory usage snould remain constant, once the JVM is fully operational.
      ACTUAL -
      The memory size grows from 8mb to over 600mb when running the test program.

      ERROR MESSAGES/STACK TRACES THAT OCCUR :
      None


      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      public class TestMe {
        public static void main(String args[]) {
        long numExceptions = 0L;
        String str = "";
        Object o = str;
        for (int i = 0; i < 10000000; i++) {
         try {
          double x = ((Number)o).doubleValue();
         } catch (ClassCastException ex) {
          numExceptions++;
         }
        }
        System.out.println("numExceptions="+numExceptions);
       }
      }

      ---------- END SOURCE ----------

      CUSTOMER SUBMITTED WORKAROUND :
      public class TestMe {
        public static void main(String args[]) {
        long numExceptions = 0L;
        String str = "";
        Object o = str;
        for (int i = 0; i < 10000000; i++) {
         try {
          if (o instanceof Number) {
           double x = ((Number)o).doubleValue();
          }
         } catch (ClassCastException ex) {
          numExceptions++;
         }
        }
        System.out.println("numExceptions="+numExceptions);
       }
      }

      However, there may be other cases where Exception objects are being created for which sucn a workaround is not sufficient.

      Release Regression From : 5.0u12
      The above release value was the last known release where this
      bug was not reproducible. Since then there has been a regression.

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            • Assignee:
              xlu Xiaobin Lu (Inactive)
              Reporter:
              ndcosta Nelson Dcosta (Inactive)
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              • Created:
                Updated:
                Resolved:
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