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      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 
     17 package 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  */
     45 public 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 void destroy() {
     52             // Don't call super.destroy().
     53             // It's a shared object.  We don't want the mDestroyed to be set on this.
     54         }
     55 
     56         @Override public boolean isList() {
     57             return false;
     58         }
     59 
     60         @Override public boolean isString() {
     61             return false;
     62         }
     63 
     64         @Override public String toString() {
     65             return "[NO ELEMENT]";
     66         }
     67 
     68         @Override
     69         public boolean equalsForTest(ImapElement that) {
     70             return super.equalsForTest(that);
     71         }
     72     };
     73 
     74     private boolean mDestroyed = false;
     75 
     76     public abstract boolean isList();
     77 
     78     public abstract boolean isString();
     79 
     80     protected boolean isDestroyed() {
     81         return mDestroyed;
     82     }
     83 
     84     /**
     85      * Clean up the resources used by the instance.
     86      * It's for removing a temp file used by {@link ImapTempFileLiteral}.
     87      */
     88     public void destroy() {
     89         mDestroyed = true;
     90     }
     91 
     92     /**
     93      * Throws {@link RuntimeException} if it's already destroyed.
     94      */
     95     protected final void checkNotDestroyed() {
     96         if (mDestroyed) {
     97             throw new RuntimeException("Already destroyed");
     98         }
     99     }
    100 
    101     /**
    102      * Return a string that represents this object; it's purely for the debug purpose.  Don't
    103      * mistake it for {@link ImapString#getString}.
    104      *
    105      * Abstract to force subclasses to implement it.
    106      */
    107     @Override
    108     public abstract String toString();
    109 
    110     /**
    111      * The equals implementation that is intended to be used only for unit testing.
    112      * (Because it may be heavy and has a special sense of "equal" for testing.)
    113      */
    114     public boolean equalsForTest(ImapElement that) {
    115         if (that == null) {
    116             return false;
    117         }
    118         return this.getClass() == that.getClass(); // Has to be the same class.
    119     }
    120 }
    121