1 /*
   2  * Copyright (c) 2010, 2013, 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 
  26 package com.sun.tools.doclets.internal.toolkit;
  27 
  28 import java.io.IOException;
  29 import java.io.StringWriter;
  30 import java.io.Writer;
  31 import java.util.Objects;
  32 
  33 import com.sun.tools.doclets.internal.toolkit.util.*;
  34 
  35 /**
  36  * A class to create content for javadoc output pages.
  37  *
  38  *  <p><b>This is NOT part of any supported API.
  39  *  If you write code that depends on this, you do so at your own risk.
  40  *  This code and its internal interfaces are subject to change or
  41  *  deletion without notice.</b>
  42  *
  43  * @author Bhavesh Patel
  44  */
  45 public abstract class Content {
  46 
  47     /**
  48      * Returns a string representation of the content.
  49      *
  50      * @return string representation of the content
  51      */
  52     @Override
  53     public String toString() {
  54         StringWriter out = new StringWriter();
  55         try {
  56             write(out, true);
  57         } catch (IOException e) {
  58             // cannot happen from StringWriter
  59             throw new DocletAbortException(e);
  60         }
  61         return out.toString();
  62     }
  63 
  64     /**
  65      * Adds content to the existing content.
  66      *
  67      * @param content content that needs to be added
  68      */
  69     public abstract void addContent(Content content);
  70 
  71     /**
  72      * Adds a string content to the existing content.
  73      *
  74      * @param stringContent the string content to be added
  75      */
  76     public abstract void addContent(String stringContent);
  77 
  78     /**
  79      * Writes content to a writer.
  80      *
  81      */
  82     public abstract boolean write(Writer writer, boolean atNewline) throws IOException ;
  83 
  84     /**
  85      * Returns true if the content is empty.
  86      *
  87      * @return true if no content to be displayed else return false
  88      */
  89     public abstract boolean isEmpty();
  90 
  91     /**
  92      * Returns true if the content is valid.
  93      *
  94      * @return true if the content is valid else return false
  95      */
  96     public boolean isValid() {
  97         return !isEmpty();
  98     }
  99 
 100     /**
 101      * Return the number of characters of plain text content in this object
 102      * (optional operation.)
 103      * @return the number of characters of plain text content in this
 104      */
 105     public int charCount() {
 106         return 0;
 107     }
 108 
 109     /**
 110      * Checks for null values.
 111      *
 112      * @param t reference type to check for null values
 113      * @return the reference type if not null or else throws a null pointer exception
 114      */
 115     protected static <T> T nullCheck(T t) {
 116         return Objects.requireNonNull(t);
 117     }
 118 }