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.lang3.builder; 018 019/** 020 * <p> 021 * The Builder interface is designed to designate a class as a <em>builder</em> 022 * object in the Builder design pattern. Builders are capable of creating and 023 * configuring objects or results that normally take multiple steps to construct 024 * or are very complex to derive. 025 * </p> 026 * 027 * <p> 028 * The builder interface defines a single method, {@link #build()}, that 029 * classes must implement. The result of this method should be the final 030 * configured object or result after all building operations are performed. 031 * </p> 032 * 033 * <p> 034 * It is a recommended practice that the methods supplied to configure the 035 * object or result being built return a reference to {@code this} so that 036 * method calls can be chained together. 037 * </p> 038 * 039 * <p> 040 * Example Builder: 041 * <pre><code> 042 * class FontBuilder implements Builder<Font> { 043 * private Font font; 044 * 045 * public FontBuilder(String fontName) { 046 * this.font = new Font(fontName, Font.PLAIN, 12); 047 * } 048 * 049 * public FontBuilder bold() { 050 * this.font = this.font.deriveFont(Font.BOLD); 051 * return this; // Reference returned so calls can be chained 052 * } 053 * 054 * public FontBuilder size(float pointSize) { 055 * this.font = this.font.deriveFont(pointSize); 056 * return this; // Reference returned so calls can be chained 057 * } 058 * 059 * // Other Font construction methods 060 * 061 * public Font build() { 062 * return this.font; 063 * } 064 * } 065 * </code></pre> 066 * 067 * Example Builder Usage: 068 * <pre><code> 069 * Font bold14ptSansSerifFont = new FontBuilder(Font.SANS_SERIF).bold() 070 * .size(14.0f) 071 * .build(); 072 * </code></pre> 073 * 074 * 075 * @param <T> the type of object that the builder will construct or compute. 076 * 077 * @since 3.0 078 * @version $Id: Builder.java 1583482 2014-03-31 22:54:57Z niallp $ 079 */ 080public interface Builder<T> { 081 082 /** 083 * Returns a reference to the object being constructed or result being 084 * calculated by the builder. 085 * 086 * @return the object constructed or result calculated by the builder. 087 */ 088 T build(); 089}