DEV Community: Jagadeesh

JS Code Snippets

Jagadeesh — Sat, 29 Jan 2022 05:48:19 +0000

Array

1. Find an element in an array using `find()` method.

let numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

let number = numbers.find(_number => _number === 8);
console.log(number);    // 8

number = numbers.find(_number => _number === 80);
console.log(number);    // undefined

2. tbd

3. tbd

4. tbd

Blocking/NonBlocking or Synchronus/Asynchronus Code

Synchronus or Blocking code

console.log('Before');
console.log('After');

// Result
// Before
// After

Asynchronus or NonBlocking code

console.log('Before');

setTimeout(() => {
    console.log('Reading a user from DB...')
}, 2000);

console.log('After');

// Result
// Before
// After
// Reading a user from DB...

setTimeout() schedules for future run. In this case after 2sec, there will be a console message.

It's not a multithread or parallel run. Still it's a single thread run and due to scheduling, execution is not blocked.

Callback
Promises
Async/Await (syntactic over promise)

1. Callback

2. Promises

3. Async/Await

hello, world!

Jagadeesh — Thu, 06 Jan 2022 19:34:10 +0000

JS
console.log('hello, world!');

# include <stdio.h>

int main(void)
{
  printf("hello, world!");
}

Oracle JDK 17 is FREE now.

Jagadeesh — Sun, 03 Oct 2021 06:05:28 +0000

Official announcement from Oracle

Hi everyone! There is a good news for all the Java developers and all the customers using Java under a commercial license : Oracle JDK is available for free starting from JDK 17 (published just few days ago).
With a post on the Oracle Blog on September 14th, Donald Smith (Sr. Director of Product Management) gives us this news, introducing the Java free license. Here is a resume of the post.
This free license includes the JDK and the quarterly security updates also for commercial and production use. The new license is the “Oracle No-Fee Terms and Conditions” (NFTC) license and permits free use for all users, even commercial and production use. Redistribution is permitted as long as it is not for a fee.
Developers and organizations can now easily download, use, share and redistribute the Oracle JDK without needing a click-through. Oracle will provide these free releases and updates starting with Oracle JDK 17 and continue for one full year after the next LTS release.
Prior versions are not affected by this change. Oracle will continue to provide Oracle OpenJDK releases under the GPL on the same releases and schedule as it has since Java 9.
In September 2017, Oracle announced plans to distribute the JDK under the GPL as “Oracle OpenJDK” and also as the Oracle JDK under an Oracle Technology Network (OTN) license.
Providing Oracle OpenJDK builds under the GPL was highly welcomed, but feedback from developers, academia and enterprises was that they wanted the trusted, rock-solid Oracle JDK under an unambiguously free terms license, too.
Oracle appreciates the feedback from the developer ecosystem and are pleased to announce that as of Java 17 we are delivering on exactly that request.
Oracle will provide Oracle JDK LTS releases under the NFTC for at least one full year after the subsequent LTS version, giving you more flexibility on your upgrade schedules.
You can still follow the six monthly JDK release cadence to benefit from faster access to new features, performance improvements and other enhancements, of course, but you now also have the time necessary to migrate from one Oracle JDK LTS to the next, if that’s the model that you prefer.
The Oracle Java SE Subscription continues to provide value-added features such as the Java Management Service, Advanced Management Console and GraalVM Enterprise at no incremental cost.
Coupled with 24x7 support (from the very developers at Oracle who develop source code for most of the Java platform used globally) and the low cost of just $25 (USD)/month/processor or $2.50(USD)/user/month, the Oracle Java SE Subscription remains a high value choice favored by thousands of organizations small and large alike.
What do you think about this news?

Reference:
https://www.youtube.com/watch?v=XVZFpw3X4lI
https://www.oracle.com/java/technologies/downloads/
https://www.oracle.com/java/technologies/java-se-support-roadmap.html

Integer Palindrome

Jagadeesh — Tue, 23 Feb 2021 07:56:21 +0000

PALINDROME INTEGER

KEYWORDS / QUESTIONS
`num % 10 - Get right most number.` `num / 10 - Remove right most number.`

NOTES

Number palindrome.
A palindrome is a word, phrase, number, or sequence of words that reads the same backward as forward. The straightforward solution would be to convert numbers to string and use the PalindromeString approach.
There are two most important things to remember.
To get the most right number, we can do 'num % 10'.
To remove most right number, we can do 'num / 10'.
Both will work for any numbers.

Steps:

Loop through num till it becomes zero.
Get the most right number.
First multiply by 10. Later concat with the rightmost number(do not add)
Remove most right number from num.
If reversed version and original are equal so it's a palindrome

Time Complexity: O(n)

'remainder = num % 10;' here when num will become less than 10 expression will return that number so that's how program copying last(first) number
'num = num / 10;' here when num will become less than 10 expression will make it 0 and program will exit from the loop

Implementation

package com.playground;

public class PalindromeInteger {

    public static boolean isPal(int num) {
        int copyOfOriginal = num;
        int reversedNumber = 0;
        int remainder;

        // 1. Loop through num till it becomes zero.
        while (num > 0) {
            // 2. Get most right number.
            remainder = num % 10;

            // 3. First multiply by 10. Later concat with right most number(do not add)
            reversedNumber = (reversedNumber * 10) + remainder;

            // 4. Remove most right number from num.
            num = num / 10;
        }

        // 5. If reversed version and original are equal so it's palindrome
        return reversedNumber == copyOfOriginal;
    }
}

Test

package com.playground;

import com.playground.PalindromeInteger;
import org.junit.Assert;
import org.junit.Test;

public class PalindromeIntegerTest {

    @Test
    public void withValidPalInt() {
        Assert.assertEquals(PalindromeInteger.isPal(242), true);
    }

    @Test
    public void withNonPalInt() {
        Assert.assertEquals(PalindromeInteger.isPal(243), false);
    }

    @Test
    public void withSingleInt() {
        Assert.assertEquals(PalindromeInteger.isPal(2), true);
    }

    @Test
    public void withTwoInt() {
        Assert.assertEquals(PalindromeInteger.isPal(40), false);
    }

    @Test
    public void withTwoPalInt() {
        Assert.assertEquals(PalindromeInteger.isPal(44), true);
    }

}

Reference:
- https://beknazarsuranchiyev.medium.com/top-17-java-coding-interview-questions-for-sdet-a978754eb078

SUMMARY
There are two most important things to remember.
To get the most right number, we can do 'num % 10'.
To remove most right number, we can do 'num / 10'.
Both will work for any numbers.

Why Selenium WebDriver is an Interface?

Jagadeesh — Wed, 17 Feb 2021 12:24:57 +0000

WEBDRIVER INTERFACE

KEYWORDS / QUESTIONS
`Interface WebDriver` `ChromeDriver` `ChromeDriverService`
`System.setPropert(key, value)`
`chromedriver` `geckodriver` `msedgedriver` `phantomjs`
`WebDriver driver;` `driver = new ChromeDriver();` `driver = new FirefoxDriver();`

NOTES

All browser specific classes (ChromeDriver, FirefoxDriver etc) implemented a common interface called WebDriver interface. info

WebDriver interface contains commonly used methods for browser automation.

Ex:

WebDriver Methods

Return Type	Methods
void	close()
WebElement	findElement(By by)
java.util.List	findElements(By by)
void	get(java.lang.String url)
java.lang.String	getTitle()
tbd	tbd

We can create different browser object using same object type WebDriver.

Ex:

WebDriver driver;

driver = new ChromeDriver();

driver = new FirefoxDriver();

package io.webdriver.chrome;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.chrome.ChromeDriverService;
import org.openqa.selenium.edge.EdgeDriver;
import org.openqa.selenium.edge.EdgeDriverService;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.openqa.selenium.firefox.GeckoDriverService;
import org.openqa.selenium.phantomjs.PhantomJSDriver;
import org.openqa.selenium.phantomjs.PhantomJSDriverService;

import java.io.File;

public class WebDriverInterface {
    public static void main(String[] args) {
        WebDriver driver;

        System.setProperty(ChromeDriverService.CHROME_DRIVER_EXE_PROPERTY, getDriver("chromedriver").getAbsolutePath());
        System.setProperty(GeckoDriverService.GECKO_DRIVER_EXE_PROPERTY, getDriver("geckodriver").getAbsolutePath());
        System.setProperty(EdgeDriverService.EDGE_DRIVER_EXE_PROPERTY, getDriver("msedgedriver").getAbsolutePath());
        System.setProperty(PhantomJSDriverService.PHANTOMJS_EXECUTABLE_PATH_PROPERTY, getDriver("phantomjs").getAbsolutePath());


        driver = new ChromeDriver();
        System.out.println(driver.toString());
        driver.quit();

        driver = new FirefoxDriver();
        System.out.println(driver.toString());
        driver.quit();

        driver = new EdgeDriver();
        System.out.println(driver.toString());
        driver.quit();

        driver = new PhantomJSDriver();
        System.out.println(driver.toString());
        driver.quit();
    }

    /**
     * Based on the OS, we get browser driver location.
     *
     * @param driverName a string. ex: "chromedriver"
     * @return the relative (partial) path of the driver. ex: driver/chromedriver
     */
    private static File getDriver(String driverName) {
        if (System.getProperty("os.name").contains("Mac OS X")) {
            return new File(new File("driver"), driverName);
        } else {
            return new File(new File("driver"), driverName + ".exe");
        }
    }

}

ChromeDriver: chrome on WINDOWS (24a35fb050dc5e8d46ba8c0eede0eb1f)
FirefoxDriver: firefox on WINDOWS (413c13b1-7984-41e4-a7cc-a31b85438e71)
EdgeDriver: msedge on WINDOWS (83af823aa10d801182ad9726e3ed911b)
PhantomJSDriver: phantomjs on XP (01d457b0-7114-11eb-a16e-d3a30713c1eb)

SUMMARY
WebDriver is an Interface.
ChromeDriver, FirefoxDriver etc classes implemented WebDriver interface.
WebDriver has common methods for all browsers. Ex: get(), getTitle(), findElement() etc

DEV Community: Jagadeesh

JS Code Snippets

Array

1. Find an element in an array using find() method.

2. tbd

3. tbd

4. tbd

Blocking/NonBlocking or Synchronus/Asynchronus Code

1. Callback

2. Promises

3. Async/Await

hello, world!

Oracle JDK 17 is FREE now.

Integer Palindrome

PALINDROME INTEGER

NOTES

Why Selenium WebDriver is an Interface?

WEBDRIVER INTERFACE

NOTES

1. Find an element in an array using `find()` method.