FULL PRODUCT VERSION :
java version "1.8.0_112"
Java(TM) SE Runtime Environment (build 1.8.0_112-b15)
Java HotSpot(TM) 64-Bit Server VM (build 25.112-b15, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

EXTRA RELEVANT SYSTEM CONFIGURATION :
with eclipse Mars 2 
and with apache ant

A DESCRIPTION OF THE PROBLEM :
The ClassCastException is thrown on the same line of code:

      Double val = (Double)0.23f;

sometimes with message:

"java.lang.Float cannot be cast to java.lang.Double"

and sometimes with null message

REGRESSION.  Last worked in version 6u45

ADDITIONAL REGRESSION INFORMATION: 
java version "1.8.0_112"
Java(TM) SE Runtime Environment (build 1.8.0_112-b15)
Java HotSpot(TM) 64-Bit Server VM (build 25.112-b15, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
run the code snippet:

       public Integer g(Object data)
       {
           try
           {
               Double d = (Double)data;
           }
           catch(ClassCastException ex)
           {
            if( ex.getMessage() == null )
            {
              return 1;
            }
           }
           return 0;
       }

       @Test
       public void h()
       {
              Integer count = 0;
              for( Integer idx = 0; idx < 100000; idx++ )
              {
                     // The test
                     count += g(0.7312345f);
              }
              System.out.println("Total ClassCastException's with null message: "+count);
       }

and notice that much of the times the message in the exception is null

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
the counter should be 0


ACTUAL -
88k (out of 100k) were with null message of the ClassCastException

REPRODUCIBILITY :
This bug can be reproduced often.

---------- BEGIN SOURCE ----------
run the code snippet:

       public Integer g(Object data)
       {
           try
           {
               Double d = (Double)data;
           }
           catch(ClassCastException ex)
           {
            if( ex.getMessage() == null )
            {
              return 1;
            }
           }
           return 0;
       }

       @Test
       public void h()
       {
              Integer count = 0;
              for( Integer idx = 0; idx < 100000; idx++ )
              {
                     // The test
                     count += g(0.7312345f);
              }
              System.out.println("Total ClassCastException's with null message: "+count);
       }

and notice that much of the times the message in the exception is null
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
workaround is to add -Xint to JVM flags to work in interpreter mode but this slows the processing substantially of course

note that when debugger is attached in eclipse - this phenomenon does not occur - maybe the code is interpreted when debugger is attached...