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/*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.contacts.common;
import android.content.Context;
import java.util.Iterator;
import java.util.List;
/**
* Class used for collapsing data items into groups of similar items. The data items that should be
* collapsible should implement the Collapsible interface. The class also contains a utility
* function that takes an ArrayList of items and returns a list of the same items collapsed into
* groups.
*/
public final class Collapser {
/*
* The Collapser uses an n^2 algorithm so we don't want it to run on
* lists beyond a certain size. This specifies the maximum size to collapse.
*/
private static final int MAX_LISTSIZE_TO_COLLAPSE = 20;
/*
* This utility class cannot be instantiated.
*/
private Collapser() {}
/**
* Collapses a list of Collapsible items into a list of collapsed items. Items are collapsed if
* {@link Collapsible#shouldCollapseWith(Object)} returns true, and are collapsed through the
* {@Link Collapsible#collapseWith(Object)} function implemented by the data item.
*
* @param list List of Objects of type <T extends Collapsible<T>> to be collapsed.
*/
public static <T extends Collapsible<T>> void collapseList(List<T> list, Context context) {
int listSize = list.size();
// The algorithm below is n^2 so don't run on long lists
if (listSize > MAX_LISTSIZE_TO_COLLAPSE) {
return;
}
for (int i = 0; i < listSize; i++) {
T iItem = list.get(i);
if (iItem != null) {
for (int j = i + 1; j < listSize; j++) {
T jItem = list.get(j);
if (jItem != null) {
if (iItem.shouldCollapseWith(jItem, context)) {
iItem.collapseWith(jItem);
list.set(j, null);
} else if (jItem.shouldCollapseWith(iItem, context)) {
jItem.collapseWith(iItem);
list.set(i, null);
break;
}
}
}
}
}
// Remove the null items
Iterator<T> itr = list.iterator();
while (itr.hasNext()) {
if (itr.next() == null) {
itr.remove();
}
}
}
/*
* Interface implemented by data types that can be collapsed into groups of similar data. This
* can be used for example to collapse similar contact data items into a single item.
*/
public interface Collapsible<T> {
void collapseWith(T t);
boolean shouldCollapseWith(T t, Context context);
}
}
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