java hashmap example

Java Collection framework 08 -- HashMap and source code analysis1. Introduction to HashMap First, let's take a look at the inheritance relationship of HashMap. java.lang.Object ? java.util.AbstractMap ? java.util.HashMap public class HashMap

. put ("B", "bbb "); Tab. put ("c", "ccc "); Tab. put ("d", "ddd "); Iterator While (iterator_1.hasNext ()){ Object key = iterator_1.next (); System. out. println ("tab. get (key) is:" + tab. get (key )); } TreeMap Tmp. put ("a", "aaa "); Tmp. put ("B", "bbb "); Tmp. put ("c", "ccc "); Tmp. put ("d", "cdc "); Iterator While (iterator_2.hasNext ()){ Object key = iterator_2.next (); System. out. println ("tmp. get (key) is:" + tmp. get (key )); } } } The running result is as follows:Map. get (key)

What is HashMap?HashMap is a non-synchronous implementation based on the Map interface of the hash table. This implementation provides all optional ing operations and allows the use of null values and null keys. This class does not guarantee the order of mappings, especially it does not guarantee that the order remains unchanged.Java HashMapJava's HashMap consist

HashMap quickly find its content through hashcode, and all elements in TreeMap remain in a fixed order, and if you need to get an ordered result you should use TREEMAP (the order of the elements in HashMap is not fixed).HashMap non-thread-safe TreeMap non-thread safeThread SafetyIn Java, thread safety generally manifes

0. Foreword The difference between HashMap and Hashtable a relatively simple answer is: (1) HashMap is not thread-safe, Hashtable is thread-safe. (2) HashMap's keys and values allow NULL to exist, while Hashtable is not. (3) HashMap efficiency is higher than hashtable because of the problem of thread safety and hash efficiency. But if you keep asking: What is an

elements), and then compute the array subscript, and finally in Createentry () using the head interpolation method to insert the element. Get operation Public V get (Object key) { if (key = null) return getfornullkey (); entry This is simpler than put (), which also determines whether the key is null and then the traversal query of the linked list. Performance optimization HashMap is an efficient and versatile data structure th

you can search for the correct list. A Data Structure like this is called a hash table (hashtable ).HashTables in JavaJava contains two classes: Java. util. hashtable and Java. util. hashmap. They provide a hashtable mechanism for multiple purposes. These two classes are very similar and generally provide the same public interface. But they do have some importan

First, let's introduce what map is. In the array we index the contents by an array, and in the map we index the object by object, and the object used for indexing is called key, and its corresponding object is called value. This is what we normally say as key-value pairs.HashMap the contents of the hashcode by a quick lookup, and treemap all the elements are in a certain order, if you need to get an orderly result you should use TreeMap (HashMap in th

Let's start by describing what a map is. In the array we index the content by the array subscript, and in the map we index the object by object, the object to index is called key, and its corresponding object is called value. This is what we call a key-value pair.HashMap quickly find its content through hashcode, and all elements in TreeMap remain in a fixed order, and if you need to get an ordered result you should use TREEMAP (the order of the elements in