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 */ 017 018package org.apache.commons.text.lookup; 019 020import java.util.function.BiFunction; 021import java.util.function.Function; 022 023/** 024 * Lookups a String key for a String value. 025 * <p> 026 * This class represents the simplest form of a string to string map. It has a benefit over a map in that it can create 027 * the result on demand based on the key. 028 * </p> 029 * <p> 030 * For example, it would be possible to implement a lookup that used the key as a primary key, and looked up the value 031 * on demand from the database. 032 * </p> 033 * <p> 034 * Like {@link BiFunction} is a variant of {@link Function}, this {@code BiStringLookup} is a variant of 035 * {@link StringLookup}. 036 * </p> 037 * 038 * @param <U> The second argument type. 039 * 040 * @since 1.9 041 */ 042@FunctionalInterface 043public interface BiStringLookup<U> extends StringLookup { 044 045 /** 046 * Looks up a String key to provide a String value. 047 * <p> 048 * The internal implementation may use any mechanism to return the value. The simplest implementation is to use a 049 * Map. However, virtually any implementation is possible. 050 * </p> 051 * <p> 052 * For example, it would be possible to implement a lookup that used the key as a primary key, and looked up the 053 * value on demand from the database Or, a numeric based implementation could be created that treats the key as an 054 * integer, increments the value and return the result as a string - converting 1 to 2, 15 to 16 etc. 055 * </p> 056 * <p> 057 * This method always returns a String, regardless of the underlying data, by converting it as necessary. For 058 * example: 059 * </p> 060 * 061 * <pre> 062 * Map<String, Object> map = new HashMap<String, Object>(); 063 * map.put("number", new Integer(2)); 064 * assertEquals("2", StringLookupFactory.biFunctionStringLookup(map).lookup("number", "A context object")); 065 * </pre> 066 * 067 * @param key the key to look up, may be null. 068 * @param object ignored by default. 069 * @return The matching value, null if no match. 070 */ 071 default String lookup(final String key, final U object) { 072 return lookup(key); 073 } 074 075}