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Showing posts from June, 2016

MongoDB Overview

         MongoDB is an open-source document database, and leading NoSQL database. MongoDB is written in c++.                MongoDB is a cross-platform, document oriented database that provides, high performance, high availability,   and easy scalability.                 MongoDB works on concept of collection and document. Database Database is a physical container for collections. Each database gets its own set of files on the file system. A single MongoDB server typically has multiple databases. Collection Collection is a group of MongoDB documents. It is the equivalent of an RDBMS table. A collection exists within a single database. Collections do not enforce a schema. Documents within a collection can have different fields. Typically, all documents in a collection are of similar or related purpose. Document A document is a set of key-value pairs. Document...

HashMap in Java

    -What is HashMap:       A HashMap has value and  key. store value based on Key. HasMap implements the Map interface and extends AbstractMap class.       Allow only one null as key and can contain   multiple null value.       Also Conatin Order of element.         HasMap----extend---->AbstractMap----implement---->Map                 Now we see how to Put and Retrive value from HashMap.                Example.             import java.util.*;               class MapTest{                        public static void main(String args[]){     HashMap<Integer,String> map=new HashMap<Integer,String>();     map.put(1,"vjp");   map.put(...