Java Data StructuresLesson 62Free preview

Java ArrayList

This lesson is part of Java · All levels

Summary

ArrayList is a List implementation that is stored as a dynamic array and automatically enlarges when capacity runs out. Access using indexes such as get and set is very fast, while insertion or deletion in the middle is slower because the elements have to be moved. This structure is most often used for data that is more read than modified.

Key points

It can grow dynamically; new ArrayList<>(starting capacity) saves redistribution
The get/set index-based operation runs O(1), while the add-center and remove-center O(n)
The main method: add, remove(index), remove(obj), set, get, contains, size
Allowing the null element and maintaining duplicates
Not thread-safe; for multithreaded environments use Collections.synchronizedList()

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