| /* |
| * 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.text.lookup; |
| |
| import java.util.Map; |
| import java.util.Objects; |
| import java.util.function.Function; |
| |
| /** |
| * A function-based lookup where the request for a lookup is answered by applying that function with a key. |
| * |
| * @param <V> A function's input type |
| * |
| * @since 1.9 |
| */ |
| final class FunctionStringLookup<V> extends AbstractStringLookup { |
| |
| /** |
| * Creates a new instance backed by a Function. |
| * |
| * @param <R> the function's input type |
| * @param function the function, may be null. |
| * @return a new instance backed by the given function. |
| */ |
| static <R> FunctionStringLookup<R> on(final Function<String, R> function) { |
| return new FunctionStringLookup<>(function); |
| } |
| |
| /** |
| * Creates a new instance backed by a Map. Used by the default lookup. |
| * |
| * @param <V> the map's value type. |
| * @param map the map of keys to values, may be null. |
| * @return a new instance backed by the given map. |
| */ |
| static <V> FunctionStringLookup<V> on(final Map<String, V> map) { |
| return on(StringLookupFactory.toMap(map)::get); |
| } |
| |
| /** |
| * Function. |
| */ |
| private final Function<String, V> function; |
| |
| /** |
| * Creates a new instance backed by a Function. |
| * |
| * @param function the function, may be null. |
| */ |
| private FunctionStringLookup(final Function<String, V> function) { |
| this.function = function; |
| } |
| |
| /** |
| * Looks up a String key by applying the function. |
| * <p> |
| * If the function is null, then null is returned. The function result object is converted to a string using |
| * toString(). |
| * </p> |
| * |
| * @param key the key to be looked up, may be null. |
| * @return The function result as a string, may be null. |
| */ |
| @Override |
| public String lookup(final String key) { |
| if (function == null) { |
| return null; |
| } |
| final V obj; |
| try { |
| obj = function.apply(key); |
| } catch (final SecurityException | NullPointerException | IllegalArgumentException e) { |
| // Squelched. All lookup(String) will return null. |
| // Could be a ConcurrentHashMap and a null key request |
| return null; |
| } |
| return Objects.toString(obj, null); |
| } |
| |
| @Override |
| public String toString() { |
| return super.toString() + " [function=" + function + "]"; |
| } |
| |
| } |