In Java, a HashMap is a class that implements the Map interface and stores key-value pairs using a hash table data structure. It allows you to store keys of any object type and retrieve the corresponding values using those keys.
A hash table, on the other hand, is a data structure that uses a hash function to map keys to indices in an array, and stores key-value pairs in the array. A hash table can be implemented in different ways, and a HashMap is one such implementation.
There are several differences between HashMap and a hash table:
- HashMap is a class in Java, whereas a hash table is a data structure.
- HashMap is part of the java.util package, while a hash table is a more general concept that can be implemented in different ways.
- HashMap allows null keys and null values, while a hash table may or may not allow null keys and values, depending on the implementation.
- HashMap uses a hashing function to map keys to indices, while a hash table may use a different method to map keys to indices.
- HashMap provides additional methods for modifying the map, such as put, get, and remove, which are not available in a hash table.
Overall, HashMap is a specific implementation of a hash table in Java that offers additional functionality for storing and retrieving key-value pairs.
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