code: public Throwable getException(String exceptionClassName) throws ExceptionInstantiationException {
          if (exceptionClassName == null) {
              return null;
          }
  
          Throwable ex = null;
          if (previousExceptionInfo != null) {
              if (previousExceptionInfo.getClassName().equals(exceptionClassName)) {
                  ex = getPreviousException();
              } else {
                  ex = previousExceptionInfo.getException(exceptionClassName);
              }
          }
          return ex;
      }
docs: Get a specific exception in a possible chain of exceptions.
  If there are multiple exceptions in the chain, the most recent one thrown
  will be returned.
  If the exceptions does not exist or no exceptions have been chained,
  null will be returned.
  
  @exception com.ibm.websphere.exception.ExceptionInstantiationException
  An exception occurred while trying to instantiate an exception object.
  If this exception is thrown, the relevant information can be retrieved
  using the getPreviousExceptionInfo() method.
  
  @param String exceptionClassName the class name of the specific exception.
  @return java.lang.Throwable The specific exception in a chain of
  exceptions. If no exceptions have been chained, null will be returned.