Get Size of a Map

 
import java.util.Map;
import java.util.TreeMap;

public class Main {
  public static void main(String[] args) {
    Map<String, String> treeMap = new TreeMap<String, String>();
    System.out.println("Size of TreeMap : " + treeMap.size());

    treeMap.put("1", "One");
    treeMap.put("2", "Two");
    treeMap.put("3", "Three");

    System.out.println("Size of TreeMap after addition : " + treeMap.size());
    treeMap.remove("2");
    System.out.println("Size of TreeMap after removal : " + treeMap.size());

  }

}