Collections Notes

The helper methods that save writing loops, and a practical way to pick the right collection every time.

Comparable gives a class one natural order. Comparator supplies any number of orders from outside, without touching the class.

Java

An Iterator walks a collection one element at a time, and it is the only safe way to remove during a traversal.

Java

A Queue processes elements in an order it decides. A Deque works at both ends, and it is the right way to build a stack in Java.

Java

Buckets, hashing, collisions and resizing. Understanding the mechanism explains the performance and every rule about keys.

Java

A Map stores key to value pairs with unique keys, and it is the collection you will reach for most often.

Java

A Set stores unique elements. The three implementations differ in ordering and in what uniqueness is based on.

Java

A List keeps insertion order and allows duplicates. ArrayList is the default; LinkedList wins only at the ends.

Java

A small set of interfaces describes how groups of objects behave, and many implementations trade memory, ordering and speed differently.