Java collection (review)

Fengx、 2021-05-04 00:12:13
java collection review


Concept

  • Design around a set of standard interfaces , Is a unified architecture for representing and manipulating collections

Include content

Interface

  • Manipulating independent sets represents details

Realization ( class )

  • Implementation interface , reusable

Algorithm

  • polymorphic , Different sets have the same method ( Insert , Sort, etc ) There are different implementations

chart

Interface

Collection

  • List

    • Inherit Collection And a List Instances store elements of an ordered collection
  • Set

    • A collection that does not contain repeating elements

    • SortedSet

      • Inherit Set, Keep an orderly collection
  • Queue

Map

  • Map unique keys to values ( key / It's worth it )

  • SortedMap

    • Inherited from Map, send Key Keep in ascending order

Iterator

Collection classes

Java Provides a set of implementations Collection The standard collection class of the interface

List

  • LinkedList

    • Inherited from AbstractSequentialList( Inherited from AbstractList), Implement a linked list

      • Realization List Interface
      • To realize two-way linked list (Deque) structure , Easy to insert data head and tail
      • Implementation queue (Queue) Interface , fifo
    • The default size is 10, Every time 1.5 times

  • ArrayList

    • Inherited from AbstractList, Implementation of dynamic array

      • Solve the limitations of arrays

      • Common methods

        • add

        • remove

        • size

          • size
      • ArrayList Realization List Interface , A common way to write a reference is to declare it as List type

      • Specify generics , Only the specified elements and their subclasses can be stored ; It is not specified that any type can be stored

      • Traverse

        • for
        • iterator
        • Enhanced for loop
      • Array construction

  • difference

    • ArrayList

      • Insert , Delete slowly , Quick query ( Sequential structure )
    • LinkedList

      • Insert , Delete fast , Slow query ( Chain table structure )
  • stack

  • vector

Set

  • HashSet

    • Inherited from AbstractSet, And use a hash table

      • Elements cannot be repeated

      • Elements are inserted in no order

      • Traverse

        • iterator
        • Enhanced for loop
      • And HashMap Relationship

        • The interior encapsulates one Map
  • LinkedHashSet

    • Inherited from HashSet
    • Having predictable order of iterations Set Interface hash table and link list implementation
  • TreeSet

    • Inherited AbstractSet, Sort elements using their natural order
    • TreeSet You can ensure that the collection elements are in a sorted state

CopyonWriteArrayList and CopyOnWriteArraySet

  • principle : Read / write separation , Read supports high concurrency , Writing needs locking

  • problem

    • Memory footprint
    • Data consistency issues , Support ultimate consistency , Real time consistency is not supported

Map

  • HashMap

    • How to store data

      • Key value pair

        • key only , Do not repeat , The value is repeatable
    • Inherited HashMap, And a hash table is used

    • Non thread safe class

    • JDK7: Array + Linked list

    • JDK8: Array + Linked list + Red and black trees

    • HashMap1.7 Why is the head insertion method used ,1.8 After using the tail insertion method , Does this change have any effect

      • jdk8 Before hashmap In the concurrent scenario, if multiple threads are expanded at the same time, a circular list will appear

      • HashMap stay jdk1.8 Then the concept of red black tree was introduced ,
        Indicates that if the linked list element in the bucket exceeds 8 when , It will automatically turn into a red black tree ;
        If the element in the barrel is less than or equal to 6 when , The tree structure is reduced to the form of a linked list .

        • choice 6 and 8 Why

          • There's a difference in the middle 7 It can prevent frequent conversion between linked list and tree
      • Insecurity mainly occurs during capacity expansion , Easy to produce circular list

    • ConcurrentHashMap

      • 1.7 And 1.8 The difference between

        • 1.8 Use Unsafe Class CAS Spin assignment +synchronized Sync +
          LockSupport Blocking and other means to achieve efficient concurrency

          • Head insertion
  • LinkedHashMap

    • Inherited from HashMap, Sort elements using their natural order
  • HashTable

    • Thread safety class
  • TreeMap

    • Inherited AbstractMap, And used a tree

Binary tree

structure

  • Root node , Each root node has a left child node , The right child node

Sort

  • Left order

    • Root left and right
  • Middle preface

    • Left root right
  • Right order

    • Left and right
版权声明
本文为[Fengx、]所创,转载请带上原文链接,感谢
https://javamana.com/2021/05/20210504001148488n.html

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