How HashMap Works in Java
Understanding How HashMap Works in Java
How HashMap Works in Java
In Java, a HashMap is a data structure that stores key-value pairs and allows for fast retrieval of values based on their corresponding keys. The HashMap uses a hashing function to convert the key into an index within an array to efficiently store and retrieve the values. When a key-value pair is added to the HashMap, the key is hashed and the resulting index is used to store the value in the corresponding location in the array. If there is a collision (i.e., two keys hash to the same index), a linked list or a binary search tree is used to store multiple entries at the same index. This allows for constant-time average-case performance for insertion, deletion, and lookup operations, making HashMap a popular choice for storing and retrieving data in Java applications.
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1 - HashMap in Java is a data structure that stores key value pairs.
2) It is a part of the Java Collections Framework and is available in the java.util package.
3) It uses a technique called hashing to store and retrieve elements quickly.
4) In a HashMap, keys are unique and do not allow duplicates.
5) Keys in a HashMap are used to calculate the hash code, which determines the index where the corresponding value will be stored.
6) HashMap allows null keys and null values.
7) It is not synchronized, meaning it is not thread safe by default.
8) HashMap uses an array of buckets or slots to store key value pairs.
9) To avoid collision, HashMap uses separate chaining or open addressing.
10) HashMap has methods like `put(key, value)`, `get(key)`, `remove(key)`, `containsKey(key)`, and `containsValue(value)` for basic operations.
11) The capacity and load factor of a HashMap can be specified to control its performance and memory usage.
12) The default initial capacity of a HashMap is 16.
13) The load factor determines when the HashMap should resize and rehash its elements.
14) Resizing and rehashing help in maintaining a low collision rate and efficient performance.
15) Understanding how HashMap works is essential for efficient data retrieval and storage in Java applications.
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