Discussion
What will be the output of the program?
import java.util.*;
public class Case32
{
public static void main(String[] args)
{
Map<String, String> m = new Hashtable<String, String>();
m.put("k", null);
System.out.println(m.size());
}
}
Answer: D
Hashtable is the legacy synchronised map and permits neither a null key nor a null value, throwing NullPointerException on either. HashMap allows one null key and any number of null values, which is the distinction being drawn.
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