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 package 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 * <code><pre>
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 * </pre></code>
066 *
067 * Example Builder Usage:
068 * <code><pre>
069 * Font bold14ptSansSerifFont = new FontBuilder(Font.SANS_SERIF).bold()
070 * .size(14.0f)
071 * .build();
072 * </pre></code>
073 * </p>
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 1088899 2011-04-05 05:31:27Z bayard $
079 */
080 public 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 public T build();
089 }