firstKey(): It returns the key from TreeMap which have the least value(Key having lowest value) . It returns null if TreeMap is empty.
import java.util.TreeMap;
class ExampleOfTreeMap
{
public static void main(String arg[])
{
TreeMap<Integer, String> listOfNames = new TreeMap<Integer, String>();
listOfNames.put(3, "C");
listOfNames.put(1, "A");
listOfNames.put(2, "D");
listOfNames.put(6, "B");
listOfNames.put(8, "B");
// It return the Key having least Key of TreeMap
System.out.println("Least Key of TreeMap :"+listOfNames.firstKey());
}
}
Output: Least Key of TreeMap :1
