ImapElement.java revision ff0712cb1e2e1902d754ac37ab637b94b8cc8933 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.email.mail.store.imap;
18
19/**
20 * Class representing "element"s in IMAP responses.
21 *
22 * <p>Class hierarchy:
23 * <pre>
24 * ImapElement
25 *   |
26 *   |-- ImapElement.NONE (for 'index out of range')
27 *   |
28 *   |-- ImapList (isList() == true)
29 *   |   |
30 *   |   |-- ImapList.EMPTY
31 *   |   |
32 *   |   --- ImapResponse
33 *   |
34 *   --- ImapString (isString() == true)
35 *       |
36 *       |-- ImapString.EMPTY
37 *       |
38 *       |-- ImapSimpleString
39 *       |
40 *       |-- ImapMemoryLiteral
41 *       |
42 *       --- ImapTempFileLiteral
43 * </pre>
44 */
45public abstract class ImapElement {
46    /**
47     * An element that is returned by {@link ImapList#getElementOrNone} to indicate an index
48     * is out of range.
49     */
50    public static final ImapElement NONE = new ImapElement() {
51        @Override public boolean isList() {
52            return false;
53        }
54
55        @Override public boolean isString() {
56            return false;
57        }
58
59        @Override public String toString() {
60            return "[NO ELEMENT]";
61        }
62
63        @Override
64        public boolean equalsForTest(ImapElement that) {
65            return super.equalsForTest(that);
66        }
67    };
68
69    public abstract boolean isList();
70
71    public abstract boolean isString();
72
73    /**
74     * Clean up the resources used by the instance.
75     * It's for removing a temp file used by {@link ImapTempFileLiteral}.
76     */
77    public void destroy() {
78    }
79
80    /**
81     * Return a string that represents this object; it's purely for the debug purpose.  Don't
82     * mistake it for {@link ImapString#getString}.
83     *
84     * Abstract to force subclasses to implement it.
85     */
86    @Override
87    public abstract String toString();
88
89    /**
90     * The equals implementation that is intended to be used only for unit testing.
91     * (Because it may be heavy and has a special sense of "equal" for testing.)
92     */
93    public boolean equalsForTest(ImapElement that) {
94        if (that == null) {
95            return false;
96        }
97        return this.getClass() == that.getClass(); // Has to be the same class.
98    }
99}
100