import java.util.HashMap;

public class Test {

  public static void main(String[] args) {

    HashMap<String, Integer> map = new HashMap<>();
    map.put("ABC", 3); // put some values in
    map.put("DEF", 27);
    map.put("GHI", 5);
    String test = "DEF";
    if (map.containsKey(test)) { // if present
      map.put(test, map.get(test) + 1); // change value
    }
    System.out.println(map.get(test)); // check - 28

  }
}