Zak Dyer

Zak Dyer


Learn and Understand the FileWriter class

1. FileWriter

FileWriter is a specialized OutputStreamWriter for writing character files. It doesn’t expose any new operations but works with the operations inherited from the OutputStreamWriter and Writer classes.

Until Java 11, the FileWriter worked with the default character encoding and default byte buffer size. However, Java 11 introduced four new constructors that accept a Charset, thereby allowing user-specified Charset. Unfortunately, we still cannot modify the byte buffer size, and it’s set to 8192.

1.1. Instantiating the FileWriter

There are five constructors in the FileWriter class if we’re using a Java version before Java 11.

Let’s have a glance at various constructors:

public FileWriter(String fileName) throws IOException {
    super(new FileOutputStream(fileName));
public FileWriter(String fileName, boolean append) throws IOException {
    super(new FileOutputStream(fileName, append));
public FileWriter(File file) throws IOException {
    super(new FileOutputStream(file));
public FileWriter(File file, boolean append) throws IOException {
    super(new FileOutputStream(file, append));
public FileWriter(FileDescriptor fd) {
    super(new FileOutputStream(fd));

Java 11 introduced four additional constructors:

public FileWriter(String fileName, Charset charset) throws IOException {
    super(new FileOutputStream(fileName), charset);
public FileWriter(String fileName, Charset charset, boolean append) throws IOException {
    super(new FileOutputStream(fileName, append), charset);
public FileWriter(File file, Charset charset) throws IOException {
    super(new FileOutputStream(file), charset);
public FileWriter(File file, Charset charset, boolean append) throws IOException {
    super(new FileOutputStream(file, append), charset);

1.2. Writing a _String _to a File

Let’s now use one of the FileWriter constructors to create an instance of FileWriter and then write to a file:

try (FileWriter fileWriter = new FileWriter("src/test/resources/FileWriterTest.txt")) {
    fileWriter.write("Hello Folks!");

We’ve used the single argument constructor of the FileWriter that accepts a file name. We then use the write(String str) operation inherited from the _Writer _class. Since the FileWriter is AutoCloseable, we’ve used try-with-resources so that we don’t have to close the FileWriter explicitly.

On executing the above code, the String will be written to the specified file:

Hello Folks!

The FileWriter does not guarantee whether the FileWriterTest.txt file will be available or be created. It is dependent on the underlying platform.

We must also make a note that certain platforms may allow only a single FileWriter instance to open the file. In that case, the other constructors of the FileWriter class will fail if the file involved is already open.

1.3. Appending a _String _to a File

We often need to append data to the existing contents of a file. Let’s now see an example of a FileWriter that supports appending:

try (FileWriter fileWriter = new FileWriter("src/test/resources/FileWriterTest.txt", true)) {
    fileWriter.write("Hello Folks Again!");

As we can see, we’ve used the two-argument constructor that accepts a file name and a boolean flag append. Passing the flag append as true creates a FileWriter that allows us to append text to existing contents of a file.

On executing the code, we’ll have the String appended to the existing contents of the specified file:

Hello Folks!Hello Folks Again!

2. Conclusion

In this article, we learned about the convenience class FileWriter and a couple of ways in which the FileWriter can be created. We then used it to write data to a file.

As always, the complete source code for the tutorial is available over on GitHub.


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Learn and Understand the FileWriter class
Lawrence  Lesch

Lawrence Lesch


Superdom: Better and Simpler ES6 DOM Manipulation


You have dom. It has all the DOM virtually within it. Use that power:

// Fetch all the page links
let links = dom.a.href;

// Links open in a new tab = '_blank';

Only for modern browsers

Getting started

Simply use the CDN via

<script src=""></script>

Or use npm or bower:

npm|bower install superdom --save


It always returns an array with the matched elements. Get all the elements that match the selector:

// Simple element selector into an array
let allLinks = dom.a;

// Loop straight on the selection
dom.a.forEach(link => { ... });

// Combined selector
let importantLinks = dom['a.important'];

There are also some predetermined elements, such as id, class and attr:

// Select HTML Elements by id:
let main =;

// by class:
let buttons = dom.class.button;

// or by attribute:
let targeted =;
let targeted = dom.attr['target="_blank"'];


Use it as a function or a tagged template literal to generate DOM fragments:

// Not a typo; tagged template literals
let link = dom`<a href="">Google</a>`;

// It is the same as
let link = dom('<a href="">Google</a>');

Delete elements

Delete a piece of the DOM

// Delete all of the elements with the class .google
delete;   // Is this an ad-block rule?


You can easily manipulate attributes right from the dom node. There are some aliases that share the syntax of the attributes such as html and text (aliases for innerHTML and textContent). There are others that travel through the dom such as parent (alias for parentNode) and children. Finally, class behaves differently as explained below.

Get attributes

The fetching will always return an array with the element for each of the matched nodes (or undefined if not there):

// Retrieve all the urls from the page
let urls = dom.a.href;     // #attr-list
  // ['', '', ...]

// Get an array of the h2 contents (alias of innerHTML)
let h2s = dom.h2.html;     // #attr-alias
  // ['Level 2 header', 'Another level 2 header', ...]

// Get whether any of the attributes has the value "_blank"
let hasBlank =;    // #attr-value
  // true/false

You also use these:

  • html (alias of innerHTML): retrieve a list of the htmls
  • text (alias of textContent): retrieve a list of the htmls
  • parent (alias of parentNode): travel up one level
  • children: travel down one level

Set attributes

// Set target="_blank" to all links = '_blank';     // #attr-set
dom.class.tableofcontents.html = `
  <ul class="tableofcontents">
    ${ => `
        <a href="#${}">

Remove an attribute

To delete an attribute use the delete keyword:

// Remove all urls from the page
delete dom.a.href;

// Remove all ids


It provides an easy way to manipulate the classes.

Get classes

To retrieve whether a particular class is present or not:

// Get an array with true/false for a single class
let isTest = dom.a.class.test;     // #class-one

For a general method to retrieve all classes you can do:

// Get a list of the classes of each matched element
let arrays = dom.a.class;     // #class-arrays
  // [['important'], ['button', 'cta'], ...]

// If you want a plain list with all of the classes:
let flatten = dom.a.class._flat;     // #class-flat
  // ['important', 'button', 'cta', ...]

// And if you just want an string with space-separated classes:
let text = dom.a.class._text;     // #class-text
  // 'important button cta ...'

Add a class

// Add the class 'test' (different ways)
dom.a.class.test = true;    // #class-make-true
dom.a.class = 'test';       // #class-push

Remove a class

// Remove the class 'test'
dom.a.class.test = false;    // #class-make-false


Did we say it returns a simple array?

dom.a.forEach(link => link.innerHTML = 'I am a link');

But what an interesting array it is; indeed we are also proxy'ing it so you can manipulate its sub-elements straight from the selector:

// Replace all of the link's html with 'I am a link'
dom.a.html = 'I am a link';

Of course we might want to manipulate them dynamically depending on the current value. Just pass it a function:

// Append ' ^_^' to all of the links in the page
dom.a.html = html => html + ' ^_^';

// Same as this:
dom.a.forEach(link => link.innerHTML = link.innerHTML + ' ^_^');

Note: this won't work dom.a.html += ' ^_^'; for more than 1 match (for reasons)

Or get into genetics to manipulate the attributes: = '_blank';

// Only to external sites:
let isOwnPage = el => /^https?\:\/\/mypage\.com/.test(el.getAttribute('href')); = (prev, i, element) => isOwnPage(element) ? '' : '_blank';


You can also handle and trigger events:

// Handle click events for all <a> = e => ...;

// Trigger click event for all <a>;


We are using Jest as a Grunt task for testing. Install Jest and run in the terminal:

grunt watch

Download Details:

Author: franciscop
Source Code: 
License: MIT license

#javascript #es6 #dom 

Yashi Tyagi


CA Classes - Best CA Classes Online

Chartered Accountancy course requires mental focus & discipline, coaching for CA Foundation, CA Inter and CA Finals are omnipresent, and some of the best faculty’s classes have moved online, in this blog, we are going to give the best way to find online videos lectures, various online websites provide the CA lectures, Smartnstudy one of the best site to CA preparation, here all faculty’s video lecture available.

check here : ca classes

#ca classes online #ca classes in delhi #ca classes app #ca pendrive classes #ca google drive classes #best ca classes online

Jerad  Bailey

Jerad Bailey


Google Reveals "What is being Transferred” in Transfer Learning

Recently, researchers from Google proposed the solution of a very fundamental question in the machine learning community — What is being transferred in Transfer Learning? They explained various tools and analyses to address the fundamental question.

The ability to transfer the domain knowledge of one machine in which it is trained on to another where the data is usually scarce is one of the desired capabilities for machines. Researchers around the globe have been using transfer learning in various deep learning applications, including object detection, image classification, medical imaging tasks, among others.

#developers corner #learn transfer learning #machine learning #transfer learning #transfer learning methods #transfer learning resources

sophia tondon

sophia tondon


5 Latest Technology Trends of Machine Learning for 2021

Check out the 5 latest technologies of machine learning trends to boost business growth in 2021 by considering the best version of digital development tools. It is the right time to accelerate user experience by bringing advancement in their lifestyle.

#machinelearningapps #machinelearningdevelopers #machinelearningexpert #machinelearningexperts #expertmachinelearningservices #topmachinelearningcompanies #machinelearningdevelopmentcompany

Visit Blog-

#machine learning companies #top machine learning companies #machine learning development company #expert machine learning services #machine learning experts #machine learning expert

Jackson  Crist

Jackson Crist


Intro to Reinforcement Learning: Temporal Difference Learning, SARSA Vs. Q-learning

Reinforcement learning (RL) is surely a rising field, with the huge influence from the performance of AlphaZero (the best chess engine as of now). RL is a subfield of machine learning that teaches agents to perform in an environment to maximize rewards overtime.

Among RL’s model-free methods is temporal difference (TD) learning, with SARSA and Q-learning (QL) being two of the most used algorithms. I chose to explore SARSA and QL to highlight a subtle difference between on-policy learning and off-learning, which we will discuss later in the post.

This post assumes you have basic knowledge of the agent, environment, action, and rewards within RL’s scope. A brief introduction can be found here.

The outline of this post include:

  • Temporal difference learning (TD learning)
  • Parameters
  • QL & SARSA
  • Comparison
  • Implementation
  • Conclusion

We will compare these two algorithms via the CartPole game implementation. This post’s code can be found here :QL code ,SARSA code , and the fully functioning code . (the fully-functioning code has both algorithms implemented and trained on cart pole game)

The TD learning will be a bit mathematical, but feel free to skim through and jump directly to QL and SARSA.

#reinforcement-learning #artificial-intelligence #machine-learning #deep-learning #learning