Content.java revision 3233:b5d08bc0d224 
1/*
2 * Copyright (c) 2010, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package jdk.javadoc.internal.doclets.toolkit;
27
28import java.io.IOException;
29import java.io.StringWriter;
30import java.io.Writer;
31import java.util.Objects;
32
33import jdk.javadoc.internal.doclets.toolkit.util.DocletAbortException;
34
35
36/**
37 * A class to create content for javadoc output pages.
38 *
39 *  <p><b>This is NOT part of any supported API.
40 *  If you write code that depends on this, you do so at your own risk.
41 *  This code and its internal interfaces are subject to change or
42 *  deletion without notice.</b>
43 *
44 * @author Bhavesh Patel
45 */
46public abstract class Content {
47
48    /**
49     * Returns a string representation of the content.
50     *
51     * @return string representation of the content
52     */
53    @Override
54    public String toString() {
55        StringWriter out = new StringWriter();
56        try {
57            write(out, true);
58        } catch (IOException e) {
59            // cannot happen from StringWriter
60            throw new DocletAbortException(e);
61        }
62        return out.toString();
63    }
64
65    /**
66     * Adds content to the existing content.
67     *
68     * @param content content that needs to be added
69     */
70    public abstract void addContent(Content content);
71
72    /**
73     * Adds a string content to the existing content.
74     *
75     * @param stringContent the string content to be added
76     */
77    public abstract void addContent(String stringContent);
78
79    /**
80     * Writes content to a writer.
81     *
82     */
83    public abstract boolean write(Writer writer, boolean atNewline) throws IOException ;
84
85    /**
86     * Returns true if the content is empty.
87     *
88     * @return true if no content to be displayed else return false
89     */
90    public abstract boolean isEmpty();
91
92    /**
93     * Returns true if the content is valid.
94     *
95     * @return true if the content is valid else return false
96     */
97    public boolean isValid() {
98        return !isEmpty();
99    }
100
101    /**
102     * Return the number of characters of plain text content in this object
103     * (optional operation.)
104     * @return the number of characters of plain text content in this
105     */
106    public int charCount() {
107        return 0;
108    }
109
110    /**
111     * Checks for null values.
112     *
113     * @param t reference type to check for null values
114     * @return the reference type if not null or else throws a null pointer exception
115     */
116    protected static <T> T nullCheck(T t) {
117        return Objects.requireNonNull(t);
118    }
119}
120