public static <T> T checkNotNull(T reference, @Nullable Object errorMessage) {
		if (reference == null) {
			throw new IllegalArgumentException(String.valueOf(errorMessage));
		}
		return reference;
	}
Ensures that an object reference passed as a parameter to the calling method is not null.

@param <T>          type
@param reference    an object reference
@param errorMessage the exception message to use if the check fails; will be converted to a string using
                    {@link String#valueOf(Object)}
@return the non-null reference that was validated
ngrinder-core/src/main/java/org/ngrinder/common/util/Preconditions.java