hashmap implementation in java

1, Hashtable is a dictionary subclass, Copy Code code as follows: public class HashtableExtends dictionaryImplements Map HASHMAP: Copy Code code as follows: public class HashmapExtends abstractmapImplements Map HashMap and Hashtable are all the implementation classes of the map interface; 2, the method in Hashtable is sync

, Hashtable also uses the enumeration approach in detail:Map map = new HashMap (), Map.put ("A", "N"), Map.put ("B", "n"), Map.put ("C", "N"); Iterator iter = Map.entryset (). Iterator (); while (Iter.hasnext ()) { Map.entry Entry = (map.entry) iter.next (); Object key = Entry.getkey (); Object val = Entry.getvalue ();} or for (Map.entry Entry:map.entrySet ()) { Object key = Entry.getkey (); Object value = Entry.getvalue ();}Why do

quickly through the hash function.The Hashcode method in Java is to map the object-related information (such as the object's storage address, the object's field, and so on) into a numeric value, which is called a hash, according to certain rules.Back to see, hashcode corresponds to the key code value of keys, and then we put the Java code in the string hashcode calculation code to see:The hashcode is actua

values.Where key and value are objects and cannot contain duplicate keys, they can contain duplicate value.In Hashtable, null values are not allowed for key and value.In HashMap, NULL can be a key, with only one key, and a value of one or more keys to null. When the Get () method returns a null value, it may be that the key is not in the hashmap, or it may cause the value of the key to be null. Therefore,

the use and traversal of HashMap in JavaCategory: Algorithms and data Structures 2011-10-19 10:53 5345 people read reviews (0) favorite reports Hashmapjavastringobjectiteratorlist1: A simple example of using HashMap[Java]View Plaincopy Package com.pb.collection; Import Java.util.HashMap; Import Java.util.Iterator; Import Java.util.Set; Import J

.Hashtable supports iterator and enumeration two ways of traversing . 5) Different initial capacity and expansion modethe default capacity of the HashMap is twice times the capacity of the original, when expanding;the default capacity of the Hashtable is one, and the capacity is changed to twice timesthe original +1.6) The hash value algorithm for adding key-value is differentHashMap When adding elements, a custom hashing algorithm is used ;Hashtable

The analysis of a storage class is nothing more than two points: the data structure used for storage and the operating mechanism of storage. Data structure: Array [Java]/*** The table, resized as necessary. Length MUST Always be a power of two.*/Transient Entry [] table; /*** The table, resized as necessary. Length MUST Always be a power of two.*/Transient Entry [] table;Entry Linked List format. That is, HashMap