Remove duplicate values from HashMap in Java

Question

I have a map with duplicate values:

(\"A\", \"1\");
(\"B\", \"2\");
(\"C\", \"2\");
(\"D\", \"3\");
(\"E\", \"3\");

I would like to the map

Answer 1

This can be done using Java 8. The concept of stream is required. The pseudocode, is stream().filter().collect(). If the Initial Map : {A=1, B=2, C=2, D=3, E=3}. Then the required answer after removing the duplicates is {A=1, B=2, D=3} .

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;

public class RemoveDuplicates1 {
   public static void main(String[] args) {

        //Initial Map : {A=1, B=2, C=2, D=3, E=3}
        //After =>  {A=1, B=2, D=3} 

      Map map = new HashMap<>();
        map.put("A", "1");
        map.put("B", "2");
        map.put("C", "2");
        map.put("D", "3");
        map.put("E", "3");

        System.out.printf("before :   " +map );
        System.out.println("\n");

        Set set = new  HashSet<>();

        map = map.entrySet().stream()
                .filter(entry -> set.add(entry.getValue()))
                .collect(Collectors.toMap(Map.Entry :: getKey ,  Map.Entry :: getValue));
        System.out.printf("after => " + map);

   }
}