JAVA中常用的Map和Collection数据结构图解

HashMap

概述

最外层数据存储在Entry数组中，拥有相同hashcode的Entry由next属性关联

/**
     * The table, resized as necessary. Length MUST Always be a power of two.
     */
    transient Entry[] table;

HashMap内部类

static class Entry<K,V> implements Map.Entry<K,V> {
        final K key;
        V value;
        Entry<K,V> next;
        final int hash;

        /**
         * Creates new entry.
         */
        Entry(int h, K k, V v, Entry<K,V> n) {
            value = v;
            next = n;
            key = k;
            hash = h;
        }
...省略...
       
    }

图解

用箭头相连的Entry都有相同的hashcode值

ConcurrentHashMap

概述

最外层数据由Segment数组来管理，Segment中数据又由HashEntry来进行管理，最终数据是存在HashEntry对象中，拥有相同hashcode值的对象有HashEntry的next属性来进行关联

/**
     * The segments, each of which is a specialized hash table
     */
    final Segment<K,V>[] segments;

ConcurrentHashMap内部类

static final class HashEntry<K,V> {
        final K key;
        final int hash;
        volatile V value;
        final HashEntry<K,V> next;

        HashEntry(K key, int hash, HashEntry<K,V> next, V value) {
            this.key = key;
            this.hash = hash;
            this.next = next;
            this.value = value;
        }}

图解

用箭头相连的HashEntry都有相同的hashcode值

ArrayList

概述

ArrayList是由数组来存储对象的

/**
     * The array buffer into which the elements of the ArrayList are stored.
     * The capacity of the ArrayList is the length of this array buffer.
     */
    private transient Object[] elementData;

图解

LinkedList

概述

LinkedList数据是存在Entry对象里的，LikedList对象里默认会有一个名为header的Entry对象；

在向LinkedList中添加元素时，会自动修改该对象的next和previous属性，使集合中所有对象通过next和previous关联关系能形成一个闭合的环状结构

LinkedList内部类

private static class Entry<E> {
	E element;
	Entry<E> next;
	Entry<E> previous;

	Entry(E element, Entry<E> next, Entry<E> previous) {
	    this.element = element;
	    this.next = next;
	    this.previous = previous;
	}
    }

图解

以添加第一个元素后结果示例（header元素是创建LinkedList对象后就默认存在的）