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 package org.apache.commons.lang3.builder;
18
19 /**
20 * The Builder interface is designed to designate a class as a <em>builder</em>
21 * object in the Builder design pattern. Builders are capable of creating and
22 * configuring objects or results that normally take multiple steps to construct
23 * or are very complex to derive.
24 *
25 * <p>
26 * The builder interface defines a single method, {@link #build()}, that
27 * classes must implement. The result of this method should be the final
28 * configured object or result after all building operations are performed.
29 * </p>
30 *
31 * <p>
32 * It is a recommended practice that the methods supplied to configure the
33 * object or result being built return a reference to {@code this} so that
34 * method calls can be chained together.
35 * </p>
36 *
37 * <p>
38 * Example Builder:
39 * <pre>{@code
40 * class FontBuilder implements Builder<Font> {
41 * private Font font;
42 *
43 * public FontBuilder(String fontName) {
44 * this.font = new Font(fontName, Font.PLAIN, 12);
45 * }
46 *
47 * public FontBuilder bold() {
48 * this.font = this.font.deriveFont(Font.BOLD);
49 * return this; // Reference returned so calls can be chained
50 * }
51 *
52 * public FontBuilder size(float pointSize) {
53 * this.font = this.font.deriveFont(pointSize);
54 * return this; // Reference returned so calls can be chained
55 * }
56 *
57 * // Other Font construction methods
58 *
59 * public Font build() {
60 * return this.font;
61 * }
62 * }
63 * }</pre>
64 *
65 * Example Builder Usage:
66 * <pre>{@code
67 * Font bold14ptSansSerifFont = new FontBuilder(Font.SANS_SERIF).bold()
68 * .size(14.0f)
69 * .build();
70 * }</pre>
71 *
72 * @param <T> the type of object that the builder will construct or compute.
73 *
74 * @since 3.0
75 */
76 @FunctionalInterface
77 public interface Builder<T> {
78
79 /**
80 * Returns a reference to the object being constructed or result being
81 * calculated by the builder.
82 *
83 * @return the object constructed or result calculated by the builder.
84 */
85 T build();
86 }