Scripting Language and Programming Language

Scripting languages (JavaScript, Python , bash etc.) are interpreted at run-time. The commands written in scripting languages are read  and executed line by line . A separate program is required to read the code,interpret it and then  follow the instructions in the code. An error is issued when a line cannot be executed for any reason.   ...

Schema and User in Oracle

A schema is the set of metadata (data dictionary) used by the database, typically generated using DDL(Data Definition Language). A schema defines attributes of the database, such as  tables, columns, and properties.   A database schema is a description of the data in a database.   Consider a schema to be the user account and collection of ...

RequestProcessor Class

RequestProcessor Class is the actual place where the request processing takes place in a Struts controller environmentStruts Documentation When the request object first reaches the actionservlet class ,it invokes the process method of the underlying  RequestProcessor Class.   This process method then looks into the struts-config.xml file and tries to locate the name of the action that has come with ...

RequestDispatcher

A RequestDispatcher object can forward a client’s request to a resource or include the resource itself in the response back to the client. A resource can be another servlet, or an HTML file, or a JSP file, etc. You can also think of a RequestDispatcher object as a wrapper for the resource located at a given path ...

Preinitialization of Servlet

 A container does not initialize the servlets as soon as it starts up, it initializes a servlet when it receives a request for that servlet first time. This is called lazy loading. The servlet specification defines the element, which can be specified in the deployment descriptor to make the servlet container load and initialize the ...

Overloading and Overriding

 S.No.    Overloaded Methods  Overridden Methods  1.  Arguments  Must Change  Must not change  2.  Return Type  Can change  Can’t change except for covariant returns  3.  Exceptions  Can change  Can reduce or eliminate. Must not throw new or broader checked exception  4.  Access Modifiers  Can change  Must not make more restrictive (can be less restrictive)  5. ...

OOPs concepts 1

OOPs concepts
Object-oriented programming (OOP) is a programming paradigm that represents concepts as “objects” that have data fields (attributes that describe the object) and associated procedures known as methods.   What is an Object? An object can be considered a “thing” that can perform a set of related activities. The set of activities that the object performs ...

Null Keys or values in HashMap/Hashtable 4

Can java.util.HashMap store null key/value pair? Yes it can, However only one null key is allowed, but can store many null values against non-null keys   Example public class HashMapTest { public static void main(String args[]) { HashMap h = new HashMap(); h.put(null,null); h.put(null, "1"); h.put("1", null); h.put("1", "1"); h.put("2", null); System.out.println(h.get(null).toString()); System.out.println(h.get("1")); System.out.println(h.get("2")); } ...

NoClassDefFoundError and ClassNotFoundException

NoClassDefFoundError and ClassNotFoundException
NoClassDefFoundError is an Error ,occurs when the source  was successfully compiled but at runtime, the required class files were not found. It may also arise when the class is already loaded in different classloader(usually a parent classloader would have loaded the class and hence the class cannot be loaded again) or if an incompatible class definition ...

Microsoft Windows Briefcase

Microsoft Windows Briefcase
In Microsoft Windows, the Briefcase was a special folder that supports simple two-way file  synchronization between itself and another folder. The Briefcase is designed for mobile PC users so that they may transfer it to a removable drive and have it synchronize with the computer to which the removable drive is attached.The briefcase behaves just ...