How to use "put" function in Java.util.Map class

Question

intially an entry for key is null in a Map.
then if I try to do put function on the map with the same key which had a null value previously It doesn't allow me to put the new value for the Key.
Can anyone pleasee suggest as to how I can put a value on to key with the new value even if the old value is null.
Waiting for replies

Answer 1

I have problem with the "value"..Not with a "key"
parameter in the function.I already have a value for
Key...that is "Firstkey"
Map map = new HashMap();
String column = "FirstKey";
map.put(column, null);
The below step gives me an IllegalArgumentException
map.put(column, "FirstValue");That's not the problem. Your error is somewhere else.
This works.
public class Test {
     public static void main(String[] args) {
          Map map = new HashMap();
          String column = "FirstKey";
          map.put(column, null);
          map.put(column, "FirstValue");
          System.out.println("Done");
}Kaj