Is a particular key exists in 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>();
    treeMap.put("1", "One");
    treeMap.put("2", "Two");
    treeMap.put("3", "Three");

    System.out.println(treeMap.containsKey("1"));
  }
}