code: public static <T extends Collection<?>> T validIndex(final T collection, final int index) {
          return INSTANCE.validIndex(collection, index);
      }
docs: <p>Validates that the index is within the bounds of the argument collection; otherwise throwing an exception.</p>
  <pre>Validate.validIndex(myCollection, 2);</pre>
  <p>If the index is invalid, then the message of the exception is &quot;The validated collection index is invalid: &quot; followed by the index.</p>
  
  @param <T>
  the collection type
  @param collection
  the collection to check, validated not null by this method
  @param index
  the index to check
  
  @return the validated collection (never {@code null} for method chaining)
  
  @throws NullPointerValidationException
  if the collection is {@code null}
  @throws IndexOutOfBoundsException
  if the index is invalid
  @see #validIndex(Collection, int, String, Object...)