What are the differences between a **H...

Certainly, when discussing the differences between HashMap and Hashtable in Java, there are several key points to consider:

1. Synchronization and Thread Safety:

   • HashMap is non-synchronized, meaning it is not thread-safe and cannot be shared between multiple threads without proper synchronization code[1][2][3][4][5][6].
   • Hashtable, on the other hand, is synchronized. It is thread-safe and can be shared between multiple threads, as each method in Hashtable is synchronized[1][2][3][4][5][6].

2. Null Keys and Values:

   • HashMap allows one null key and multiple null values, which provides more flexibility in storing null entries[2][4][5][6].
   • Hashtable does not allow any null key or null value. Attempting to insert nulls into a Hashtable will result in a NullPointerException[2][4][5][6].

3. Performance:

   • Due to its non-synchronized nature, HashMap is generally faster and has higher performance in scenarios where thread safety is not a concern[4][5][6].
   • Hashtable's synchronized methods mean that it has a performance cost, which can make it slower compared to HashMap when used in a single-threaded context[4][5][6].

4. Legacy Status:

   • Hashtable is considered a legacy class as it was introduced in JDK 1.0. From JDK 1.2, it was re-engineered to implement the Map interface to become a member of the Java Collections Framework[2][5].
   • HashMap is a newer class, introduced in JDK 1.2, and was designed to be a part of the Java Collections Framework from the beginning[2][5].

5. Iterators:

   • The iterators returned by HashMap are fail-fast, meaning they will throw a ConcurrentModificationException if the map is modified while iterating over it[2][4].
   • Hashtable provides enumerations and iterators, which are not fail-fast[2].

6. Inheritance and Implementation:

   • HashMap extends the AbstractMap c...