To avoid explicitly checking for null values in Java, you can utilize certain techniques and…
In Java, both
Hashtable are used to store key-value pairs, but there are several differences between them:
- Thread Safety:
Hashtableis thread-safe, meaning it is synchronized and can be safely accessed by multiple threads concurrently. On the other hand,
HashMapis not thread-safe by default. If multiple threads access a
HashMapconcurrently, and at least one thread modifies it structurally (e.g., adding or removing entries), external synchronization is needed to ensure thread safety. However, you can use the
ConcurrentHashMapclass, which provides concurrent access without the need for external synchronization.
- Null Values and Keys:
HashMapallows null values and a single null key. In contrast,
Hashtabledoes not allow null values or null keys. If you attempt to insert a null value into a
Hashtable, it will throw a
- Performance: Due to the thread-safety overhead in
HashMapgenerally performs better in single-threaded environments.
HashMapis not synchronized by default, making it more efficient for situations where synchronization is not required.
- Iterators: The iterators provided by
HashMapare fail-fast, meaning they will throw a
ConcurrentModificationExceptionif the underlying collection is modified while iterating. In contrast, the iterators of
Hashtableare not fail-fast.
Hashtableis a legacy class that was part of the original Java collections framework. It is still supported for backward compatibility, but new code should generally use
HashMapor other newer collections classes.
Given the above differences,
HashMap is commonly used in most scenarios due to its better performance and flexibility. However, if you require thread safety or need to work with legacy code,
Hashtable can be used. Alternatively, you can consider using
ConcurrentHashMap if you require concurrent access and thread safety without the need for external synchronization.