Interested to Buy Any Domain ? << Click Here >> for more details...
why HashTable not allow null key and value
- 2 Answers
- 22296 Views
- Crimson Logic, I also Faced
- E-Mail Answers
Answers were Sorted based on User's Feedback
To successfully store and retrieve objects from a hashtable,
the objects used
as keys must implement the hashCode method and the equals
method.
In a nutshell, since null isn't an object, you can't call
.equals() or .hashCode() on it, so the Hashtable can't
compute a hash to use it as a key.
HashMap is newer, and has more advanced capabilities, which
are basically just an improvement on the Hashtable
functionality. As such, when HashMap was created, it was
specifically designed to handle null values as keys and
handles them as a special case.
Specifically, the use of null as a key is handled like this
when issuing a .get(key):
(key==null ? k==null : key.equals(k))
| Is This Answer Correct ? | 11 Yes | 1 No |
Answer / naveen
There is null check in the put method implementation of
hashtable, so it does not support null values and null keys.
public Object put(Object key, Object value) {
// Make sure the value is not null
if (value == null) throw new NullPointerException();
}
above is HashTable put method logic implemented by Sun.
| Is This Answer Correct ? | 6 Yes | 1 No |
What is meant by structural programming?
How do you calculate roots in java?
write a progam hashmap & hashtable?
Can a java program have 2 main methods?
How to sort an array in java without using sort method?
What is console based application in java?
What is the common usage of serialization? What exceptions occur during serialization?
What are the high-level thread states in java programming?
how to connect one jsp page to another jsp page????
how can u handle run time exception in java? explain with brief explanation with examples?
Can we start a thread twice in java?
Can you inherit from an abstract class java?
Core Java 
