TreeMap with Duplicate Keys 





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import java.util.Comparator;
import java.util.TreeMap;

public class TreeMapFlight {

  public static void main(String[] bag){
  TreeMap<Integer,String> tm = new TreeMap<Integer,String>(new MyComp());
  tm.put(1, "one");
  tm.put(1, "null1");
  tm.put(1, "null2");
  tm.put(1, "null3");
 
  System.out.println(tm);  
 }
}

class MyComp implements Comparator{
 @Override
 public int compare(Object o1, Object o2) {
  return 1;
 } 
}
OUTPUT
{1=one, 1=null1, 1=null2, 1=null3}

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