ConstantFactory.java
- /*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You 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.apache.commons.collections4.functors;
- import java.io.Serializable;
- import org.apache.commons.collections4.Factory;
- /**
- * Factory implementation that returns the same constant each time.
- * <p>
- * No check is made that the object is immutable. In general, only immutable
- * objects should use the constant factory. Mutable objects should
- * use the prototype factory.
- * </p>
- *
- * @param <T> the type of results supplied by this supplier.
- * @since 3.0
- */
- public class ConstantFactory<T> implements Factory<T>, Serializable {
- /** Serial version UID */
- private static final long serialVersionUID = -3520677225766901240L;
- /** Returns null each time */
- @SuppressWarnings("rawtypes") // The null factory works for all object types
- public static final Factory NULL_INSTANCE = new ConstantFactory<>(null);
- /**
- * Factory method that performs validation.
- *
- * @param <T> the type of the constant
- * @param constantToReturn the constant object to return each time in the factory
- * @return the {@code constant} factory.
- */
- public static <T> Factory<T> constantFactory(final T constantToReturn) {
- if (constantToReturn == null) {
- return NULL_INSTANCE;
- }
- return new ConstantFactory<>(constantToReturn);
- }
- /** The closures to call in turn */
- private final T iConstant;
- /**
- * Constructor that performs no validation.
- * Use {@code constantFactory} if you want that.
- *
- * @param constantToReturn the constant to return each time
- */
- public ConstantFactory(final T constantToReturn) {
- iConstant = constantToReturn;
- }
- /**
- * Always return constant.
- *
- * @return the stored constant value
- */
- @Override
- public T create() {
- return iConstant;
- }
- /**
- * Gets the constant.
- *
- * @return the constant
- * @since 3.1
- */
- public T getConstant() {
- return iConstant;
- }
- }