Interface MapConstraint<K,​V>

  • @GwtCompatible
    public interface MapConstraint<K,​V>
    A constraint on the keys and values that may be added to a Map or Multimap. For example, MapConstraints.notNull(), which prevents a map from including any null keys or values, could be implemented like this:
       public void checkKeyValue(Object key, Object value) {
         if (key == null || value == null) {
           throw new NullPointerException();

    In order to be effective, constraints should be deterministic; that is, they should not depend on state that can change (such as external state, random variables, and time) and should only depend on the value of the passed-in key and value. A non-deterministic constraint cannot reliably enforce that all the collection's elements meet the constraint, since the constraint is only enforced when elements are added.

    See Also:
    MapConstraints, Constraint
    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      void checkKeyValue​(K key, V value)
      Throws a suitable RuntimeException if the specified key or value is illegal.
      String toString()
      Returns a brief human readable description of this constraint, such as "Not null".