/**
* Copyright 2010 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package org.waveprotocol.wave.model.util;
/**
* A read only interface to a set of elements.
*
* This is used in favor of using a standard Java collections interface so that
* Javascript-optimized implementations can be used in GWT code.
*
* Null is not permitted as a value. All methods, including
* {@link #contains(Object)}, will reject null values.
*
* @author ohler@google.com (Christian Ohler)
* @author hearnden@google.com (David Hearnden)
*/
public interface ReadableIdentitySet<T> {
/**
* A procedure that accepts an element from the set.
*/
public interface Proc<T> {
void apply(T element);
}
/** @return true if and only if {@code s} is in this set. */
boolean contains(T s);
/** @return true if and only if this set is empty. */
boolean isEmpty();
/**
* @return some element in the set. If the set is empty, null is returned.
*/
T someElement();
/**
* Calls a procedure with each element in this set, in undefined order.
*/
void each(Proc<? super T> procedure);
/**
* @return the size of this set. Note: Depending on the underlying
* implementation, this may be a linear operation.
*/
int countEntries();
}