Java HASHMAP data structure and put and get methods __arcinfo

1 data structure of HASHMAP

HashMap is actually an array of linked lists, the outermost is an array, and the elements of the array are linked lists.

2 HashMap's Put method:

The source code is as follows:

<span style= "font-size:10px;"  >    Public v put (K key, V value) {       //1 If key is null put to key null position    
    if (key = null)             return Putfornullkey (value);
       //2 calculation key hash value         int hash = hash (Key.hashcode ());
       //3 get index position         int i = indexfor (hash, table.length);        //4 traversing the list of index locations, overwriting and returning old values if they exist, and if not, create a new location insert         for (ENTRY&LT;K,V&G T e = Table[i]; e!= null; E = e.next) {            Object K;            //4.1 key location has been The old value is given the new value and return the old value             if (E.hash = = Hash && (k = e.key) = = Key | | key.equ ALS (k)) {                V oldValue = e.value         &NBSP ;       E.value = value;
                e.recordaccess (this);                                  Retu
RN OldValue;             {       }        //4.2 call a If key is new
Ddentry inserts new key and value         modcount++;
        addentry (hash, key, value, I);
        return null;    }</span>

3 source code is as follows HashMap get method:

The source code is as follows:

<span style= "font-size:10px;" > Public    V get (Object key) {
        //1 if key is null to return the value of the key null directly if
        (key = null) returns
            Getfornullkey ();
        //2 calculates the hash value of the key object
        int hash = hash (Key.hashcode ());
        for (entry<k,v> e = table[indexfor (hash, table.length)];//Find the index e!= null by calculating the hash of the key
             ;
             E = e.next) {//Find traversal list Object K in index
            ;
            Find key position by equals comparison if key is found and returns value if
            (E.hash = Hash && ((k = e.key) = = Key | | key.equals (k)) return
                E.value;
        }
        return null;
    } </span>

Analysis of 4 Concurrenthashmap:

Mainly to divide the segment

Resources:

Java Improvement article (two or three)-----HASHMAP

The Concurrenthashmap of source analysis