All About Java and Interview Questions

Strategy Pattern

2011-12-29T15:37:00.000+05:30

Key points : 1. Also known as Policy pattern 2. Collection of Algos (Behavuours) 3. Algo can be selected at runtime 4. Uses composition instead of inheritance e.g. a class used for validation of incoming data may use strategy pattern in which the validation algo will be decided on the basis of data set

LimeSpot interview Question (Telephonic Interview)

2011-06-20T13:59:00.000+05:30

Currently there are three projects in LimeWire : 1. LimeWire 2. Lime Domain : Hosts domain for users 3. LIme Exchange Q1: What in an outer join and what is an Inner join? A: Inner Join returns a row when there is at-least one match in one match in both the tables. e.g. SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo FROM Persons INNER JOIN Orders ON Persons.P_Id=Orders.P_Id ORDER BY

Volatile variable in java

2011-03-13T20:17:00.000+05:30

According to Kathy Sierra : " The volatile modifier tells the JVM that a thread accessing the variable must always reconcile its own private copy of the variable with the master copy in memory " My understanding : In normal scenario, In a multi-threaded environment, every thread keeps a local copy of instance variable and if a thread makes some change to the variable, the changed value would be

The Java Class Loading Mechanism

2011-03-09T16:31:00.000+05:30

The Java platform uses a delegation model for loading classes. The basic idea is that every class loader has a "parent" class loader. When loading a class, a class loader first "delegates" the search for the class to its parent class loader before attempting to find the class itself. Constructors in java.lang.ClassLoader and its subclasses allow you to specify a parent when you instantiate a new

forward vs sendRedirect

2011-03-09T11:44:00.001+05:30

RequestDispatcher.forward() : 1) Forwards the request to some other servlet/jsp within the same application. 2) The URL in the browser does not change so the client does not get to know that the request is being sent to some other servlet. The process occurs completely within the web container 3) Request attributes are maintained 4) Faster, since everything is at the server side only

java.lang.Error

2011-03-09T10:38:00.000+05:30

Error extends Throwable. It indicates that some serious and abnormal condition has occurred and the application should not try to catch it.

Multiple catch blocks

2011-03-04T23:36:00.000+05:30

Both try{ }catch(Error e){ }catch(NullPointerException npe){ } and try{ }catch(NullPointerException npe){ }catch(Error e){ } will compile.

Exception Hierarchy

2011-03-04T23:33:00.003+05:30

Throwable is a class which extends Serializable interface. All other classes in hierarchy extend Throwable class Error , Exception and Runtime Exception classes only have the constructors (which call the corresponding super class constructors). All other methods are inherited from the Throwable class itself.

HTTP Status Codes

2011-01-25T22:31:00.000+05:30

HTTP Status Codes represent the status of response received by Client from the Server Overall range Defined range Category 100-199 100-101 Informational 200-299 200-206 Successful 300-399 300-305 Redirection 400-499 400-415 Client error 500-599 500-505 Server error

Struts - Controller

2011-01-23T13:34:00.004+05:30

In a Struts application, two components make up the Controller. These two components are the org.apache.struts.action.ActionServlet and the org.apache. struts.action.Action classes. In most Struts applications, there is one org. apache.struts.action.ActionServlet implementation and many org.apache. struts.action.Action implementations. ActionServlet acts as an Action factory by creating specific

WebApps

2011-01-22T23:12:00.000+05:30

Web applications allow compiled classes to be stored in both the /WEB−INF/classes and /WEB−INF/lib directories. Of these two directories, the class loader will load classes from the /classes directory first,followed by the JARs in the /lib directory. If you have duplicate classes in both the /classes and /lib directories, the classes in the /classes directory will take precedence.

Manage ( Enable / Disable ) startup programs in Windows Vista

2011-01-09T23:52:00.001+05:30

You can Enable / Disable startup programs on your PC with Windows Vista by following the following simple steps : 1. Go to Control Panel -> Windows Defender 2. Then go to Tools and then Software Explorer (as shown in the image below) 3. Make sure that the Category selected is 'Startup Programs'. Then select the program that you want to Disable or Remove and click the corresponding button(as

Servlet load-on-startup

2011-01-09T22:32:00.002+05:30

The value of the tag load-on-startup helps the container determine when the servlet has to be loaded. A value >=0 means that the servlet has to be loaded when the application is deployed. If the value is less than zero or if the tag element is not present, the servlet will be loaded when it is first called. Also, the order in which servlets are loaded is determined by the value of

An Unusual Paragraph

2011-01-04T22:40:00.001+05:30

This is a most unusual paragraph. How quickly can you find out what is so unusual about it? It looks so ordinary, you'd think nothing was wrong with it and in fact, nothing is wrong with it. It is unusual, why? Study it. Think about it and you may find out. If you work at it for a bit, it will dawn on you. Try to do it without coaching.