Collection

General info

• A collection is a single object representing a group of objects known as its elements.
• Six collection interfaces: Collection, Set, List, SortedSet, Map, SortedMap.
• Set
• List
• Vector
• Vector vs. ArrayList
• Map

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Set

• A group of objects with no duplication
• SortedSet -- subinterface of Set
• TreeSet -- sorted
• HashSet-- best performance, unordered.
• LinkedHashSet-- since jdk 1.4

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List

• A subinterface of Collection
• A group of objects with duplicate elements
• ArrayList -- like Vector, but its methods are not synchronized.
• LinkedList -- quick sequential access.

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Vector

• Has been retrofitted to implement List interface.
• Provides methods for working with dynamic arrays of varied element types.
• Its methods are synchronized.
• Slower access.

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Vector vs. ArrayList

• one slower, the other faster
• one has synchronized methods by default, the other is not.
• prefer ArrayList

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Map

• Maps keys and values.
• Hashtable -- historical implementation.
• SortedMap
• HashMap
• TreeMap
• LinkedHashMap
• IdentityHashMap
• WeakHashMap

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