java hashmap example

is no order, and TreeMap is in order!!) ）The following is the subject of this article. Let me give you an example of how to use HashMap:Import java.util.*; public class Exp1 {public static void Main (string[] args) { HashMap h1=new HashMap (); Random r1=new random (); for (int i=0;iUsing get () to get val

default load factor is 0.75, and we don't need to modify it in general.HashMap is a data structure that supports fast access, and it is important to understand its data structure in order to understand its performance.Third, data structureWe know that the two most commonly used structures in Java are arrays and analog pointers (references), and almost all data structures can be combined using both, HashMap

is no order, and TreeMap is in order!!) ）The following is the subject of this article. Let me give you an example of how to use HashMap:Import java.util.*; public class Exp1 {public static void Main (string[] args) { HashMap h1=new HashMap (); Random r1=new random (); for (int i=0;iUsing get () to get val

conflict, however, the new elements will be stored in the appropriate location. In this way, the actual number of calls to the equals method is greatly reduced, almost only one or two. 1. An Equal object must have an equal hash code (or hash code ). 2. If two objects have the same hashCode, they are not necessarily the same. Equals () with the same hashCode () are not necessarily equal; hashCode () with the same equals () must be equal) Please indicate the source: http://blog.csdn.net/df10128

); TreeMapNewTreemap(); Treemap.put (D1,10); Treemap.put (D2,15); Treemap.put (D3,5); Treemap.put (D4,20); for(EntryEntry:treeMap.entrySet ()) {System.out.println (Entry.getkey ()+ " - " +Entry.getvalue ()); } }}Results Print:Red dog-10Black dog-15White dog-20In this example, we sort by the size of the dog;If "Dog D4 = new Dog" ("white", 10); " is replaced with "dog D4 = new Dog" ("white", 40); ", the result will be output as follows:White dog-20R

Arraylist and hashmap are asynchronous, while vector and hashtable are synchronous. Therefore, vector and hashtable are thread-safe, while arraylist and hashmap are not thread-safe.Because synchronization takes machine time, the execution efficiency of vector and hashtable is lower than that of arraylist and hashmap. collection interface implementation class l

HashMap and HashSet are two important members of the Java Collection Framework, where HashMap is a common implementation class for the Map interface, and HashSet is a common implementation class for Set interfaces. Although HashMap and hashset implement different interface specifications, their underlying Hash storage

, which is not a bug.Data structure of HashMapHashMap mainly use arrays to store data, we all know that it will hash the key, the HA operation will have a duplicate hash value, for the hash value of the conflict, HashMap using the linked list to solve. In HashMap, there is a property declaration that says:Transient entry[] table;Entry is the class that the HashMap