java.lang.ClassCastException with null message and cause

I work on a project using Java 8

We have a negative test similar to this:

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);
}

The negative test expects the exception java.lang.ClassCastException with message "java.lang.Float cannot be cast to java.lang.Double" and it sometimes gets null message

I tried to debug it in eclipse but somehow when attached to debugger the exception and message were as expected all the time

Copyright License：
Author:「E. Levy」,Reproduced under the CC 4.0 BY-SA copyright license with link to original source & disclaimer.
Link to：https://stackoverflow.com/questions/40502576/java-lang-classcastexception-with-null-message-and-cause