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      1 /*
      2  * Copyright (C) 2009 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.contacts;
     18 
     19 import java.util.HashMap;
     20 import java.util.Iterator;
     21 import java.util.ArrayList;
     22 
     23 /**
     24  * Class used for collapsing data items into groups of similar items. The data items that should be
     25  * collapsible should implement the Collapsible interface. The class also contains a utility
     26  * function that takes an ArrayList of items and returns a list of the same items collapsed into
     27  * groups.
     28  */
     29 public final class Collapser {
     30 
     31     /*
     32      * This utility class cannot be instantiated.
     33      */
     34     private Collapser() {}
     35 
     36     /*
     37      * Interface implemented by data types that can be collapsed into groups of similar data. This
     38      * can be used for example to collapse similar contact data items into a single item.
     39      */
     40     public interface Collapsible<T> {
     41         public boolean collapseWith(T t);
     42         public boolean shouldCollapseWith(T t);
     43     }
     44 
     45     /**
     46      * Collapses a list of Collapsible items into a list of collapsed items. Items are collapsed
     47      * if {@link Collapsible#shouldCollapseWith(Object) return strue, and are collapsed
     48      * through the {@Link Collapsible#collapseWith(Object)} function implemented by the data item.
     49      *
     50      * @param list ArrayList of Objects of type <T extends Collapsible<T>> to be collapsed.
     51      */
     52     public static <T extends Collapsible<T>> void collapseList(ArrayList<T> list) {
     53 
     54         int listSize = list.size();
     55 
     56         for (int i = 0; i < listSize; i++) {
     57             T iItem = list.get(i);
     58             if (iItem != null) {
     59                 for (int j = i + 1; j < listSize; j++) {
     60                     T jItem = list.get(j);
     61                     if (jItem != null) {
     62                         if (iItem.shouldCollapseWith(jItem)) {
     63                             iItem.collapseWith(jItem);
     64                             list.set(j, null);
     65                         }
     66                     }
     67                 }
     68             }
     69         }
     70 
     71         // Remove the null items
     72         Iterator<T> itr = list.iterator();
     73         while (itr.hasNext()) {
     74             if (itr.next() == null) {
     75                 itr.remove();
     76             }
     77         }
     78 
     79     }
     80 }
     81