1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache license, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the license for the specific language governing permissions and 15 * limitations under the license. 16 */ 17 18 package org.apache.commons.text.lookup; 19 20 import java.util.function.BiFunction; 21 import java.util.function.Function; 22 23 /** 24 * Lookups a String key for a String value. 25 * <p> 26 * This class represents the simplest form of a string to string map. It has a benefit over a map in that it can create 27 * the result on demand based on the key. 28 * </p> 29 * <p> 30 * For example, it would be possible to implement a lookup that used the key as a primary key, and looked up the value 31 * on demand from the database. 32 * </p> 33 * <p> 34 * Like {@link BiFunction} is a variant of {@link Function}, this {@code BiStringLookup} is a variant of 35 * {@link StringLookup}. 36 * </p> 37 * 38 * @param <U> The second argument type. 39 * @since 1.9 40 */ 41 @FunctionalInterface 42 public interface BiStringLookup<U> extends StringLookup { 43 44 /** 45 * Looks up a String key to provide a String value. 46 * <p> 47 * The internal implementation may use any mechanism to return the value. The simplest implementation is to use a 48 * Map. However, virtually any implementation is possible. 49 * </p> 50 * <p> 51 * For example, it would be possible to implement a lookup that used the key as a primary key, and looked up the 52 * value on demand from the database Or, a numeric based implementation could be created that treats the key as an 53 * integer, increments the value and return the result as a string - converting 1 to 2, 15 to 16 etc. 54 * </p> 55 * <p> 56 * This method always returns a String, regardless of the underlying data, by converting it as necessary. For 57 * example: 58 * </p> 59 * 60 * <pre> 61 * Map<String, Object> map = new HashMap<String, Object>(); 62 * map.put("number", new Integer(2)); 63 * assertEquals("2", StringLookupFactory.biFunctionStringLookup(map).lookup("number", "A context object")); 64 * </pre> 65 * 66 * @param key the key to look up, may be null. 67 * @param object ignored by default. 68 * @return The matching value, null if no match. 69 */ 70 default String lookup(final String key, final U object) { 71 return lookup(key); 72 } 73 74 }