We will find an answer for the following questions What is StringBuilder Available Constructors Commonly used methods StringBuilder Java StringBuilder class is used to create a mutable (modifiable) string. The Java StringBuilder class is the same as the StringBuffer class except that it is non-synchronized. So its not thread-safe and can’t be Read more…
When a client visits the webapp for the first time, and HttpSession is obtained for the first time the servlet container creates a new HttpSession object, generates a long and unique ID (which you can get by session.getId()), and store it in the server’s memory. The servlet container also sets Read more…
What happens when Rest API is fired? The servlet container is attached to a web server that listens for HTTP requests on a certain port number (port 8080 for development and port 80 in production). When a client (user with a web browser) sends an HTTP request, the servlet container Read more…
What happens behind the scene when Web Application is deployed in Web Server like Tomcat? ServletContext It provides a set of methods that a servlet uses to communicate with its servlet container. There is one context per “web application” per Java Virtual Machine. A “web application” is a collection of servlets Read more…
Based on my previous posts related to Hashtable and HashMap let’s see the difference. HashMap Hashtable Non-Synchronized. Fast. Synchronized. Slow Allows one null key and any number of null values. Hashtable doesn’t allow null keys and null values. Use LinkedHashMap to maintains the insertion order. TreeMap to sort mappings based on the ascending order of Read more…
We will find out answers for the following question What is Hashtable Common methods available Hashtable HashTable is a member of the Java Collection Framework as it implements Map Interface. HashTable implements a hash table, which maps keys to values. Any non-null object can be used as a key or Read more…
We will find out answers for the following question What is HashMap in Java Common methods available HashMap HashMap is a Map-based collection class that is used to store Key & value pairs. It is denoted as HashMap<Key, Value> or HashMap<K, V>. This class makes no guarantees as to the Read more…
We will find out what are Hash functions, Hashcode, Collision and Rehashing. Since HashMap and HashSet both use Hashing Technique we will also be able to answer Internal working of HashMap Internal working of HashSet Hash functions Hash functions are used in hash tables, to quickly locate a data record (e.g., Read more…
In this Blog, we will find out How to read xls, xlsx format Excel sheet using Apache POI API How to write into an Excel sheet using Apache POI API Java doesn’t provide built-in support for working with excel files so we need to rely on Open Source APIs. I Read more…
Overview In this blog we will find answer following questions What is Overriding What is Hiding What is Overloading Overriding From javaDoc An instance method m1, declared in class C, overrides another instance method m2, declared in class A if: C is a subclass of A. The signature of m1 Read more…