code: public static String getPackageName(String fqClassName) {
  		Assert.notNull(fqClassName, "Class name must not be null");
  		int lastDotIndex = fqClassName.lastIndexOf(PACKAGE_SEPARATOR);
  		return (lastDotIndex != -1 ? fqClassName.substring(0, lastDotIndex) : "");
  	}
docs: Determine the name of the package of the given fully-qualified class name,
  e.g. "java.lang" for the {@code java.lang.String} class name.
  @param fqClassName the fully-qualified class name
  @return the package name, or the empty String if the class
  is defined in the default package