Created
September 9, 2016 13:53
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package beginnersbook.com; | |
import java.util.Collections; | |
import java.util.Comparator; | |
import java.util.HashMap; | |
import java.util.Iterator; | |
import java.util.LinkedHashMap; | |
import java.util.LinkedList; | |
import java.util.List; | |
import java.util.Map; | |
import java.util.Set; | |
public class HMapSortingByvalues { | |
public static void main(String[] args) { | |
HashMap<Integer, String> hmap = new HashMap<Integer, String>(); | |
hmap.put(5, "A"); | |
hmap.put(11, "C"); | |
hmap.put(4, "Z"); | |
hmap.put(77, "Y"); | |
hmap.put(9, "P"); | |
hmap.put(66, "Q"); | |
hmap.put(0, "R"); | |
System.out.println("Before Sorting:"); | |
Set set = hmap.entrySet(); | |
Iterator iterator = set.iterator(); | |
while(iterator.hasNext()) { | |
Map.Entry me = (Map.Entry)iterator.next(); | |
System.out.print(me.getKey() + ": "); | |
System.out.println(me.getValue()); | |
} | |
Map<Integer, String> map = sortByValues(hmap); | |
System.out.println("After Sorting:"); | |
Set set2 = map.entrySet(); | |
Iterator iterator2 = set2.iterator(); | |
while(iterator2.hasNext()) { | |
Map.Entry me2 = (Map.Entry)iterator2.next(); | |
System.out.print(me2.getKey() + ": "); | |
System.out.println(me2.getValue()); | |
} | |
} | |
private static HashMap sortByValues(HashMap map) { | |
List list = new LinkedList(map.entrySet()); | |
// Defined Custom Comparator here | |
Collections.sort(list, new Comparator() { | |
public int compare(Object o1, Object o2) { | |
return ((Comparable) ((Map.Entry) (o1)).getValue()) | |
.compareTo(((Map.Entry) (o2)).getValue()); | |
} | |
}); | |
// Here I am copying the sorted list in HashMap | |
// using LinkedHashMap to preserve the insertion order | |
HashMap sortedHashMap = new LinkedHashMap(); | |
for (Iterator it = list.iterator(); it.hasNext();) { | |
Map.Entry entry = (Map.Entry) it.next(); | |
sortedHashMap.put(entry.getKey(), entry.getValue()); | |
} | |
return sortedHashMap; | |
} | |
} |
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notice the usage of comparator in
Collections.sort
output 👍