private void assertParameterNotNull(Object parameterValue, String errorMessage) {
        if (parameterValue == null) throw new IllegalArgumentException(errorMessage);
    }
<p>
Asserts that the specified parameter value is not <code>null</code> and if it is,
throws an <code>IllegalArgumentException</code> with the specified error message.
</p>

@param parameterValue
           The parameter value being checked.
@param errorMessage
           The error message to include in the IllegalArgumentException
           if the specified parameter is null.
aws-java-sdk-s3/src/main/java/com/amazonaws/services/s3/transfer/TransferManager.java