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java programming questions that helped me during my interviews
how to generate a log file in java
import java.util.logging.Logger;
import java.util.logging.FileHandler;
import java.util.logging.SimpleFormatter;
import java.io.IOException;
class Log
{
public static void main(String[] args) {
Logger logger = Logger.getLogger("MyLog");
FileHandler fh;
try {
// This block configure the logger with handler and formatter
fh = new FileHandler("C:/Users/myworld/Desktop/MyLogFile.log");
logger.addHandler(fh);
SimpleFormatter formatter = new SimpleFormatter();
fh.setFormatter(formatter);
// the following statement is used to log any messages
logger.info("My first log");
} catch (SecurityException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
logger.info("Hi How r u?");
}
}
how to check a email is valid or not import java.util.*;
class IsValidEmailAddress
{
public boolean isValidEmailAddress(String email) {
String ePattern = "^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@((\\[[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\])|(([a-zA-Z\\-0-9]+\\.)+[a-zA-Z]{2,}))$";
java.util.regex.Pattern p = java.util.regex.Pattern.compile(ePattern);
java.util.regex.Matcher m = p.matcher(email);
return m.matches();
}
public static void main(String[] args)
{
IsValidEmailAddress valid = new IsValidEmailAddress();
System.out.println(valid.isValidEmailAddress("abc@gmail.com"));
}
}
how to generate a guid
import java.util.UUID;
public class UniqueIDTest {
public static void main(String[] args) {
UUID uniqueKey = UUID.randomUUID();
System.out.println (uniqueKey);
}
}
how to validate a phone numberimport java.util.regex.Matcher;
import java.util.regex.Pattern;
import VerhoeffAlgorithm;
class ValidationRE
{
public Boolean phoneNumberValidation( String sPhoneNumber){
//regular expression pattern for mobile number
Pattern pattern = Pattern.compile("^[2-9]{2}[0-9]{8}$");
Matcher matcher = pattern.matcher(sPhoneNumber);
if (matcher.matches()) { return true;}
else {return false; }
}
how to validate aadhar number
public static boolean validateAadharNumber(String aadharNumber){
Pattern aadharPattern = Pattern.compile("\\d{12}");
boolean isValidAadhar = aadharPattern.matcher(aadharNumber).matches();
if(isValidAadhar){
isValidAadhar = VerhoeffAlgorithm.validateVerhoeff(aadharNumber);
}
return isValidAadhar;
}
}
how to generate first n prime numbers import java.util.Scanner;
class PrimeNumberDemo
{
public static void main(String args[])
{
int n;
int status = 1;
int num = 3;
//For capturing the value of n
Scanner scanner = new Scanner(System.in);
System.out.println("Enter the value of n:");
//The entered value is stored in the var n
n = scanner.nextInt();
if (n >= 1)
{
System.out.println("First "+n+" prime numbers are:");
//2 is a known prime number
System.out.println(2);
}
for ( int i = 2 ; i <=n ; )
{
for ( int j = 2 ; j <= Math.sqrt(num) ; j++ )
{
if ( num%j == 0 )
{
status = 0;
break;
}
}
if ( status != 0 )
{
System.out.println(num);
i++;
}
status = 1;
num++;
}
}
}
how to generate String Recursive Reversal public class StringRecursiveReversal {
String reverse = "";
public String reverseString(String str){
if(str.length() == 1){
return str;
} else {
reverse += str.charAt(str.length()-1)
+reverseString(str.substring(0,str.length()-1));
return reverse;
}
}
public static void main(String a[]){
StringRecursiveReversal srr = new StringRecursiveReversal();
System.out.println("Result: "+srr.reverseString("Javatospring"));
}
}
how to generate gcd of two numbers import java.util.Scanner;
class GCD
{
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
System.out.print("enter a :");
int a = sc.nextInt();
System.out.print("enter b :");
int b = sc.nextInt();
while (a != b)
{
if(a > b)
{
a = a-b;
}
}
System.out.println("GCD : " + a);
}
}
how to generate chron jobimport java.util.Timer;
import java.util.TimerTask;
class MyTask extends TimerTask{
static int i =0;
public MyTask(){
//Some stuffs
}
@Override
public void run() {
i++;
System.out.println( i+" : Hi see you after 1 seconds");
}
}
public class CronJob{
public static void main(String[] args){
Timer t = new Timer();
MyTask mTask = new MyTask();
// This task is scheduled to run every 1 seconds
t.scheduleAtFixedRate(mTask, 0, 1000);
}
}
how to generate random password generator import java.util.Random;
public class passGen{
//Verison 1.0
private static final String dCase = "abcdefghijklmnopqrstuvwxyz";
private static final String uCase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
private static final String sChar = "!@#$%^&*";
private static final String intChar = "0123456789";
private static Random r = new Random();
private static String pass = "";
public static void main (String[] args) {
System.out.println ("Generating pass...");
while (pass.length () != 6){
int rPick = r.nextInt(4);
if (rPick == 0){
int spot = r.nextInt(25);
pass += dCase.charAt(spot);
} else if (rPick == 1) {
int spot = r.nextInt (25);
pass += uCase.charAt(spot);
} else if (rPick == 2) {
int spot = r.nextInt (7);
pass += sChar.charAt(spot);
} else if (rPick == 3){
int spot = r.nextInt (9);
pass += intChar.charAt (spot);
}
}
System.out.println ("Generated Pass: " + pass);
}
}
how to generate factorial import java.util.Scanner;
class Factorial
{
static int fact = 1;
public static void main(String[] args)
{
Scanner sc = new Scanner( System.in);
System.out.print("\nenter the number to find factorial: " );
{
fact = fact *num;
}
System.out.println( fact);
}
}
