Theprogrammersfirst: May 2017

2017-05-22

magical vowels problems

Consider following letters : a, e, i, o, u

print Magical subsequence of the string that contains all five vowels in order.

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class OnMobile {
public static int i=1;
static char getNext(){
i=i+1;
String s2="aeiou";
if(i>s2.length()){
i=i-2;
}
else if(i==s2.length()){
i=i-1;
}
return s2.charAt(i);
}
static int longestSubsequence(String s) {
Pattern pattern = Pattern.compile(".a.e.i.o.u.");
Matcher matcher = pattern.matcher(s);
boolean matchFound = matcher.matches();
if(!matchFound){
return 0;
}
int count=0;

Windows cannot be installed to this disk. The selected disk is not of the GPT partition style

Installing using the MBR or GPT partition style

"Windows cannot be installed to this disk. The selected disk is not of the GPT partition style"

Step:
Exit your Windows Setup

Press shift + f10 (command prompt will open)

Enter : diskpart

list disk

select disk 0

clean

exit

Your are done Process with windows installation

2017-05-19

java program to rotate an array n time

Rotating an array n number of time

public class ArrayRotation {
public static void main(String[] args) {
int rotate= 5;
int arr2[]={0,1,2,3,4,5,6,7,8,9,10};
int temp=0;
int a;
int b;
while(rotate!=0){
for(int i=0;i<arr2.length;i++){
if(i==0)
{
a=arr2[i];
arr2[i]=arr2[arr2.length-1];
}
else a=temp;
if(i<arr2.length-1)
b=arr2[i+1];
else b=0;
temp=b;
if(i<arr2.length-1)
arr2[i+1]=a;
System.out.print(arr2[i]+" ");
}
rotate--;
System.out.println();
}
}
}

Output

10 0 1 2 3 4 5 6 7 8 9

9 10 0 1 2 3 4 5 6 7 8

8 9 10 0 1 2 3 4 5 6 7

7 8 9 10 0 1 2 3 4 5 6

6 7 8 9 10 0 1 2 3 4 5

2017-05-17

java environment setup

download and install java ( Click to Download )

windows

admin user

Select Start, select Control Panel. double click System, and select the Advanced tab.
Or go to your computer in the address bar copy paste ( Control Panel\System and Security\System )
Click Environment Variables
In the Edit System Variable
new add variable name JAVA_HOME
variable value C:\Program Files\Java\jdk1.8.0_111
Edit PATH
Add at the end of PATH variable ; ';' symbol
add %JAVA_HOME%\bin;
Ok

Non admin user

Select Start, select Control Panel. double click System, and select the Advanced tab.
Or go to your computer in the address bar copy paste ( Control Panel\System and Security\System )
Click Environment Variables
In the Edit User Variables

Java was originally developed by James Gosling at Sun Microsystems (which has since been acquired by Oracle Corporation).

Java is "write once, run anywhere" meaning that compiled Java code can run on all platforms that support Java without the need for recompilation. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM).

2017-05-16

volatile keyword in Java best explanation

volatile Keyword use to maintain a variable in Main memory.

class text

{

static int i= 6;

}

Suppose that two threads are working on text.i
If two threads run on different processors, If one thread modifies its value the change reflect to other threads and in the original main memory.
volatile variables are not create local copy.

volatile would not be sufficient to make thread-safe, synchronization would still be needed.

Using volatile variables reduces the risk of memory, because any write to a volatile variable establishes a happens-before relationship with subsequent reads of that same variable.

This means that changes to a volatile variable are always visible to other threads.

read more about mutual exclusion, visibility and Atomic.

2017-05-11

Cryptography Engine Classes

The following engine classes are available:

SecureRandom: used to generate random or pseudo-random numbers.

SecureRandom secureRandom = new SecureRandom()
secureRandom.getInstance();
secureRandom.getInstanceStrong()

synchronized public void setSeed(byte[] seed)
public void setSeed(long seed)

synchronized public void nextBytes(byte[] bytes)

byte[] generateSeed(int numBytes)

MessageDigest: used to calculate the message digest (hash) of specified data.

Signature: initialized with keys, these are used to sign data and verify digital signatures.

Cipher: initialized with keys, these used for encrypting/decrypting data. There are various types of algorithms: symmetric bulk encryption (e.g. AES, DES, DESede, Blowfish, IDEA), stream encryption (e.g. RC4), asymmetric encryption (e.g. RSA), and password-based encryption (PBE).

Message Authentication Codes (MAC): like MessageDigests, these also generate hash values, but are first initialized with keys to protect the integrity of messages.

Introduction to Cryptography

Cryptography is the practice and study of hiding and secure information such as security, including language safety, cryptography, public key infrastructure, authentication, secure communication, and access control.

2017-05-07

java program to read text from html file

import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URL;
import java.net.URLConnection;
import java.io.*;
import java.net.*;
import javax.swing.text.*;
import javax.swing.text.html.*;
public class ReadTextFromHTML {
public static void main(String[] args) throws Exception{
EditorKit kit = new HTMLEditorKit();
Document doc = kit.createDefaultDocument();
// The Document class does not yet handle charset's properly.
doc.putProperty("IgnoreCharsetDirective", Boolean.TRUE);
// Create a reader on the HTML content.
Reader rd = getReader("http://theprogrammersfirst.blogspot.com/2016/06/javalangexception-error-getting-all.html");
// Parse the HTML.
kit.read(rd, doc, 0);
// The HTML text is now stored in the document
String s=(doc.getText(0, doc.getLength())).trim().replaceAll(" \n+", " ");
System.out.println(s);
}
static Reader getReader(String uri)
throws IOException
{
// Retrieve from Internet.
if (uri.startsWith("http:"))
{System.out.println(uri);
URLConnection conn = new URL(uri).openConnection();
return new InputStreamReader(conn.getInputStream());
}
// Retrieve from file.
else
{
return new FileReader(uri);
}
}
}

java reading xml from http

import java.io.File;
import java.net.URL;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class ReadXml {
public static void main(String[] args) {
try {
String path="http://theprogrammersfirst.blogspot.com/sitemap.xml";
DocumentBuilderFactory dbFactory
= DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(new URL(path).openStream());
doc.getDocumentElement().normalize();
System.out.println("Root element :"
+ doc.getDocumentElement().getNodeName());
NodeList nList = doc.getElementsByTagName("url");
System.out.println("----------------------------");
for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);
System.out.println("\nCurrent Element :"
+ nNode.getNodeName());
if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.println("Path - "
+ eElement
.getElementsByTagName("loc")
.item(0)
.getTextContent());
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}

Website URL name regular expression validator

Java Best Website URL name regular expression validator

public class Utility {
public static boolean isValidURL(String url)
{
String urlPattern = "^http(s{0,1})://[a-zA-Z0-9_/\\-\\.]+\\.([A-Za-z/]{2,5})[a-zA-Z0-9_/\\&\\?\\=\\-\\.\\~\\%]*";
if (url.matches(urlPattern))
return true;
else return false;
}
}

2017-05-05

Understanding Java cookies with example

Cookies are process stored data on the client computer browser and they are kept for various information tracking purpose. Static content are form server side pushed into client machine, so that its process and load data faster.

Step to Sending Cookies to the Client

Sending cookies to the client involves three steps

1. Creating a Cookie object:
You call the Cookie constructor with a cookie name and a cookie value, both of which are strings.

2. Setting the maximum age:
If you want the browser to store the cookie on disk instead of just keeping it in memory, you use setMaxAge to specify how long (in seconds) the cookie should be valid.

3. Placing the Cookie into the HTTP response headers:
You use response.addCookie to accomplish this. If you forget this step, no cookie is sent to the browser

robert bosch payslip

java static keyword best explanation

Java static keyword:
static keyword to create fields and methods that belong to the class, rather than to an instance of the class.

The static can be used in:

variable
method
block
nested class

Example:

class Test{
static int a = 10;
int b = 10;
public static void main(String args[]){

class loader Example

Java Class.forName( ) Example

irctc multiple ticket cancellation

How to cancel 2 tickets out of 4 tickets from IRCTC website?
how to cancel 1 ticket out of 2 in irctc?

Yes, It is possible .
You can cancel a single passenger from ticket from irctc

Follow these steps
Login to IRCTC

1. Go to Services > Cancel Ticket
2. Cancel E-ticket option on irctc website
3. Select the ticket and click on Cancel ticket button
(Now a window will open with passenger names and a check box on right hand side)
4. Click on the checkbox for the passengers for whom ticket is to be cancelled
5. Click on cancel ticket button below.

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