JAVA - 不能为null值

snippet.java

public static <T> T checkNotNull(T reference)
{
	if(reference == null)
		throw new NullPointerException();
	return reference;
}

public static <T> T checkNotNull(T reference, @Nullable Object errorMessage)
{
	if(reference == null)
		throw new NullPointerException(String.valueOf(errorMessage));
	return reference;
}