Mega Code Archive
Sorts map by values in ascending order
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//package sk.hasto.java.collections;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
/**
* Utility functions for working with Maps.
*
* @author Branislav Hasto
*/
public final class MapUtils {
/**
* Sorts map by values in ascending order.
*
* @param <K>
* map keys type
* @param <V>
* map values type
* @param map
* @return
*/
public static <K, V extends Comparable<V>> LinkedHashMap<K, V> sortMapByValue(
Map<K, V> map) {
List<Entry<K, V>> sortedEntries = sortEntriesByValue(map.entrySet());
LinkedHashMap<K, V> sortedMap = new LinkedHashMap<K, V>(map.size());
for (Entry<K, V> entry : sortedEntries) {
sortedMap.put(entry.getKey(), entry.getValue());
}
return sortedMap;
}
/**
* Sorts map entries by value in ascending order.
*
* @param <K>
* map keys type
* @param <V>
* map values type
* @param entries
* @return
*/
private static <K, V extends Comparable<V>> List<Entry<K, V>> sortEntriesByValue(
Set<Entry<K, V>> entries) {
List<Entry<K, V>> sortedEntries = new ArrayList<Entry<K, V>>(entries);
Collections.sort(sortedEntries, new ValueComparator<V>());
return sortedEntries;
}
/**
* Komparator podla hodnot v polozkach mapy.
*
* @param <V>
* typ hodnot
*/
private static class ValueComparator<V extends Comparable<V>> implements
Comparator<Entry<?, V>> {
public int compare(Entry<?, V> entry1, Entry<?, V> entry2) {
return entry1.getValue().compareTo(entry2.getValue());
}
}
}
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