JAVA INTERVIEW QUESTIONS

Friday, 15 February 2013

Paser String to Double:

You can parse a double value in string format to double in 4 ways.

Double.valueof(String s) : This method returns a double object containing the value invoked in it in string format.
- It can trim white-space in start or end of the string argument, by using String.trim().
- It throws NumberFormatException if the string argument is not in proper form.

Double.parseDouble(String s) : This method also returns a double instance containing the invoked string value.
- It can also trim white space in start and end of the input value, using String.trim().
- It also throws NumberFormatException if the string argument is not in proper form.

new Double(String paramString) : You a also parse a string argument containing float value by invoking it on the constructor of the Class Double. its internally using the valueof(String s) method and returns a new Double instance containing the parsed double value. So it is also using
String.trim() and throws NumberFormatException.

Fourth one, the last one is the very important one, actually its been used by all the above 3 APIs. sun.misc.FloatingDecimal.readJavaFormatString(String paramString). Its the original method used to parse a String value to decimal value. This is the actual methods, which is trimming the white space of the string, using String.trim(). It returns value in FloatingDecimal instance, so you need to cast it to double by using doubleValue(), which is another method of Class FloatingDecimal.

Below is an example which explains the above discussion:

Code:

package com.interview.question.java;

public class PaserStringToDouble {

/**

* Sample class that shows how to parse a String to double.

* @author http://interviewquestionjava.blogspot.com

public static void main(String[] args) {

// TODO Auto-generated method stub

// set a decimal value in a string with

// white space on both end.

String strValue = " 12.329 ";

// parse the string to double using

//Double.valueof(String s)

double dblValue = Double.valueOf(strValue);

// parse the string to double using

// Double.parseDouble(String s)

double dblValue2 = Double.parseDouble(strValue);

// parse the string to double using

//Double(String paramString)

Double dblValue3 = new Double(strValue);

// parse the string to double using new

// FloatingDecimal.readJavaFormatString

//(String paramString)

Double dblValue4 = new Double(sun.misc.FloatingDecimal

.readJavaFormatString(strValue).doubleValue());

// printing the outputs

System.out.println("dblValue: " + dblValue +

"\ndblValue2: " + dblValue + "\ndblValue3: " +

dblValue3 + "\ndblValue4: " + dblValue4);

}

Output:

dblValue: 12.329

dblValue2: 12.329

dblValue3: 12.329

dblValue4: 12.329

Friday, 15 February 2013 by Anijit Sarkar · 0 Read more »

Thursday, 14 February 2013

SQL (Structured Query Language) is a type of programming language, which uses to communicate with database. It’s also known as “sequel”. It provides some syntax which helps you to interact with a database. These syntax are very similar to normal English language, so it’s easy to remember and use. Now a day, all major RDBMS (Relational Database Management System) like MySQL, Oracle, postgres, MS Access and SQL Server uses SQL to maintain data.

SQL helps to store, manipulate, read and delete data from data base. It helps to performs the CRUD(Create, Read, Update & Delete) operations in RDBMS.

Create: It helps to create database, schema, table and view, along with there properties.

Read: It helps to select all information from single or multiple records from one or many table or view.

Update: It also helps us to manipulates existing data in a database.

Delete: It can also delete information or structure of database or table.

Thursday, 14 February 2013 by Anijit Sarkar · 4 Read more »

Sunday, 10 February 2013

FRAMEWORK: MVC – Model View Controller

Model-View-Controller (MVC) is a popular Software Architecture pattern widely used in web applications. It separates application data from UI (user interface) by a thin controlling layer, which actually helps as a bridge between UIs and model. In this pattern the whole application is separated in 3 layers,

1. Models are answerable for encapsulating application data, for view to present the data.

2. Views should only present this data, without involving any business logic.

3. Controllers are answerable for receiving requests from users and invoking back-end services for business process.

Sunday, 10 February 2013 by Anijit Sarkar · 3 Read more »

Monday, 28 January 2013

FRAMEWORK: WHAT IS FRAMEWORK? WHAT’S THE DIFFERENCE BETWEEN FRAMEWORK AND LIBRARY?

Framework:

A framework is a basic conceptual and reusable structure which provides generic functionality, used to solve or address complex issues.

A software framework provides basic architecture, application programming interfaces (APIs) and tools for building application and provides required infrastructure.

Library v/s Framework:

Library: Library or code library is a collection of behavior written is a specific language, which can be used to execute some function. You use it the way you want.

Framework: It controls you. You can’t deviate from the framework rules and create application.

Monday, 28 January 2013 by Anijit Sarkar · 1 Read more »

Sunday, 8 July 2012

J2EE: SERVLET: doGet() vs. doPost()

doGet():

protected void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, java.io.IOException – is a method of Class HttpServlet. It is called by the server (via the service method) to allow a servlet to handle a client's GET request.
In doGet(), the client’s request parameters are appended to the URL and sent along with header information.
doGet() is not a secured process because the request parameters are clearly visible in the URL.
Since request parameters are sent along with header information, so only a limited amount of data should be sent.