Java Data StructuresLesson 70Free preview

Java HashMap

This lesson is part of Java · All levels

Summary

HashMap is the most commonly used Map implementation because it searches for keys using hashing with average O(1). The key sequence is uncertain, and the key must have a consistent hashCode() and equals() to keep the data from getting lost. This structure is suitable for key mapping to frequently read and written values.

Key points

Get, put, and remove running average, with worst-case
Allows one key and a number of values
Not sequential; select LinkedHashMap when the input sequence needs to be maintained
The default capacity is 16 and the load factor is 0.75 before the resize occurs
The key should be immutable so that the location in the bucket does not change.

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