001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4;
018
019/**
020 * Defines a functor interface implemented by classes that perform a predicate
021 * test on an object.
022 * <p>
023 * A <code>Predicate</code> is the object equivalent of an <code>if</code> statement.
024 * It uses the input object to return a true or false value, and is often used in
025 * validation or filtering.
026 * <p>
027 * Standard implementations of common predicates are provided by
028 * {@link PredicateUtils}. These include true, false, instanceof, equals, and,
029 * or, not, method invokation and null testing.
030 *
031 * @param <T> the type that the predicate queries
032 *
033 * @since 1.0
034 */
035public interface Predicate<T> {
036
037    /**
038     * Use the specified parameter to perform a test that returns true or false.
039     *
040     * @param object  the object to evaluate, should not be changed
041     * @return true or false
042     * @throws ClassCastException (runtime) if the input is the wrong class
043     * @throws IllegalArgumentException (runtime) if the input is invalid
044     * @throws FunctorException (runtime) if the predicate encounters a problem
045     */
046    boolean evaluate(T object);
047
048}