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  1. import java.util.Comparator;
  2. import java.util.HashMap;
  3. import java.util.Map;
  4. import java.util.SortedSet;
  5. import java.util.TreeSet;
  6.  
  7. public class Main {
  8.  
  9.     public static void main(String[] args) {
  10.  
  11.         Map<String, String> map = new HashMap<String, String>();
  12.  
  13.     	map.put("My", "World!");
  14.     	map.put("Hello", "World!");
  15.     	map.put("This", "World!");
  16.     	map.put("Test", "X!");
  17.  
  18.     	System.out.println("The original map: " + map);
  19.  
  20.     	// sort the 
  21.     	SortedSet<Map.Entry<String, String>> sorted = entriesSortedByValues(map);
  22.  
  23.     	// print the value based sorted set
  24.     	System.out.println("The sorted set:   " + sorted);
  25.  
  26.         // check that for example the first element is in the set
  27.     	if (!sorted.contains(sorted.iterator().next()))
  28.         	throw new RuntimeException("The set doesn't contain the first element?");
  29.     }
  30.  
  31.     static <K,V extends Comparable<? super V>> SortedSet<Map.Entry<K,V>> entriesSortedByValues(Map<K,V> map) {
  32.         SortedSet<Map.Entry<K,V>> sortedEntries = new TreeSet<Map.Entry<K,V>>(
  33.             new Comparator<Map.Entry<K,V>>() {
  34.                 @Override public int compare(Map.Entry<K,V> e1, Map.Entry<K,V> e2) {
  35.                     int res = e1.getValue().compareTo(e2.getValue());
  36.                     return res != 0 ? res : 1; // Special fix to preserve items with equal values
  37.                 }
  38.             }
  39.         );
  40.         sortedEntries.addAll(map.entrySet());
  41.         return sortedEntries;
  42.     }
  43. }
Runtime error #stdin #stdout 0.03s 245632KB
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stdin
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Standard input is empty
stdout
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The original map: {Test=X!, My=World!, This=World!, Hello=World!}
The sorted set:   [My=World!, This=World!, Hello=World!, Test=X!]
https://ideone.com/1CPFxc
language:
Java (HotSpot 12)
created:
11 years ago
visibility:
public

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