Taogen's Blog

Development of new software products

Build the basic framework of the project.

Developing new features for existing applications. (refer to the corresponding section)

Note: Development of new software product require a lot of time to optimize the user experience and requirements. Therefore, a lot of code modifications are also required.

Developing new features for existing applications

Functional modules

Understand the software requirements.

Design data models and databases.

API design.

Detailed design.

Write unit tests and code.

Test and Fix bugs.

Modify the code due to the modification of the requirements.

Test and Fix bugs.

Data analysis modules

Understand the software requirements.

Write query statements (SQL, Elasticsearch DSL) for data statistics.

Merge query statements to reduce the number of queries.

API design.

Write the code. Define the data query and response objects and finish the code.

Test and Fix bugs.

Scheduled Tasks

Small functions

Understand the software requirements.

Modify data models and databases. (optional)

API design. (optional)

Detailed design.

Write unit tests and code.

Test and Fix bugs.

Modification of system functionality

Understand the software requirements.

Modify data models and databases. (optional)

Modify API. (optional)

Detailed design.

Modify unit tests and code.

Test and Fix bugs.

Performance Optimization

Positioning problem

Try to find the tuning approach

Software product customization (new features and modifications)

Developing new features for existing applications. (refer to the corresponding section)

Modification of system functionality. (refer to the corresponding section)

Maintain systems and miscellaneous

System troubleshooting and fixing errors.

Update data.

Import data.

Export data.

Third party service renewal.

Integrating Code Libraries

Integrating Third-Party Service API or SDK

Common third-party services

• Cloud platform
  • Storage
    • OSS
  • AI + Machine Learning
    • OCR
  • Media
    • Intelligent Media Services
• Payment. E.g. Alipay.
• Mobile Push notifications. E.g. Jiguang, Getui.
• Short Message Service (SMS)
• Social. E.g. QQ, WeChat, and Dingtalk open platform, Twitter Developer Platform, Slack API.

Providing APIs to Third-Party

Sometimes we need to redirect to our other websites without login again. In addition to single sign-on, we can also add a URL parameter to achieve automatic login.

The Process of Login By URL Parameters

The frontend requests the backend API to get the loginSign string for setting the redirect URL parameters. The redirect URL like https://xxx.com/xxx?loginSign=xxx

The backend constructs the loginSign value

• Query the redirected website username and password.
• Generate a random string.
• Get the current timestamp.
• Use the RSA public key to encrypt the username, password, timestamp, randomStr.

Return the loginSign value to frontend.

The client user clicks the redirect URL.

When the target website frontend checks that the loginSign parameter appears on the web page URL, it uses this parameter to request login automatically.

The target website backend decrypts the loginSign value, and checks the username and the password. If they are correct returns an access token, otherwise, returns an error code.

Construct the URL Parameter loginSign

Add a newline \n (ASCII 0x0A) to the end of each parameter.

username\n
password\n
timestamp\n
randomStr\n

• timestamp: the request timestamp.

Use the RSA public key to encrypt the string {username}\n{password}\n{timestamp}\n{randomStr}\n

Verify the URL Parameter loginSign

Use the RSA private key to decrypt the loginSign value.

Verify the request timestamp if it’s within 60 seconds of the current time.

Verify the username and password.

Content

• Types, Values, and Variables
• Expression, Statement, Functions
• Objects, Classes
• Arrays
• Sync
• JavaScript in Web Browsers
• Modules

Expression

Invocation Expressions

Conditional Invocation

let result = json?.name;

let result = json != null ? json.name : undefined;

Null Check

if a != null return a, else return default value

// Ternary Operator
let result = a != null ? a : defaultValue;

// Logical Operator ||
// When it's used with non-boolean values, the || operator will return a non-boolean value of one of the specified expression or operands.
let result = a || defaultValue;

// Nullish Coalescing Operator ??
let result = a ?? defaultValue;

2

if a != null and b != null return b; else return null;

let result = a != null && a.name != null ? a.name : null;

let result = a && a.name;

Statement

For Loop

for (let i = 0; i < arr.length; ++i)
arr.forEach((value, index) => { /* ... */ })
for (let index in arr)
for (const value of arr)

Print to console

console.log(obj1 [, obj2, ..., objN]);

console.log(obj)
console.log(obj1, obj2)
console.log("obj is: ", obj)
console.log("obj is: ", obj, ". And my name is ", name)
console.log("objects are: ", obj1, obj2)
console.log("obj is: " + JSON.parse(JSON.stringify(obj)))

console.log(msg [, subst1, ..., substN]);

• %o or %O Outputs a JavaScript object.
• %d or %i Outputs an integer.
• %s Outputs a string.
• %f Outputs a floating-point value.

console.log("obj is %o", obj)
console.log("Hello, %s. You've called me %d times.", "Bob", 1);

Object

Merge object fields

let json1 = {"name": "Jack"};
let json2 = {
    ...json1,
    age: 18
};

Deep copy

let json = {"name": "Jack"};
let copy = JSON.parse(JSON.stringify(json));

Get all keys of JSON/JavaScript object

const obj = {a: 'somestring', b: 123, c: false};
Object.keys(obj);

Get all values of JSON/JavaScript object

const obj = {a: 'somestring', b: 123, c: false};
Object.values(obj);

// ES6
const obj = {a: 'somestring', b: 123, c: false};
Object.keys(obj).map(key => obj[key]);

Traversing JavaScript Object

for-in

// iterates over all enumerable properties of an object.
const jsonObj = {name: "Jack", age: 18}
for (const key in jsonObj) {
  console.log(`${key}: ${jsonObj[key]}`);
}

Object.entries() or Object.keys()

// to traverse a Javascript object
const jsonObj = {name: "Jack", age: 18}
Object.entries(jsonObj).forEach(([key, value]) => {
    console.log(key, value)
});

Object.keys(obj).forEach(function(key) {
    var value = obj[key];
    // ...
});

to include non-enumerable properties

Object.getOwnPropertyNames(obj).forEach(function(key) {
    var value = obj[key];
    // ...
});

Array

Traversal

for (let i = 0; i < arr.length; ++i)
arr.forEach((value, index) => { /* ... */ })
for (let index in arr)
for (const value of arr)

forEach: executes a provided function once for each array element. another type of for loop.

NOTE: The forEach loop is another type of for loop in JavaScript. However, forEach() is actually an array method, so it can only be used exclusively with arrays. There is also no way to stop or break a forEach loop. If you need that type of behavior in your loop, you’ll have to use a basic for loop.

const array1 = ['a', 'b', 'c'];
array1.forEach(element => console.log(element));

for in: iterates over all enumerable properties of an object. E.g. key of JSON object, index of array.

const object = { a: 1, b: 2, c: 3 };

for (const property in object) {
  console.log(`${property}: ${object[property]}`);
}

for of: The for...of statement creates a loop iterating over iterable objects, including: built-in String, Array, array-like objects (e.g., arguments or NodeList), TypedArray, Map, Set, and user-defined iterables.

const array1 = ['a', 'b', 'c'];

for (const element of array1) {
  console.log(element);
}

for (const [idx, el] of arr.entries()) {
    console.log( idx + ': ' + el );
}

Summary

If you don’t need break for loop use forEach, else use for of.

Find Max in an array

Find max value in an array

// apply
const array = [{name: "a", value: 1}, {nama: "b", value: 2}]
Math.max.apply(Math, array.map(o => o.value));

const array = [1,2,3,5,1,2]
Math.max.apply(Math, array);

// ES6 spread
const array = [{name: "a", value: 1}, {nama: "b", value: 2}]
Math.max(...array.map(o => o.value));

const array = [1,2,3,5,1,2]
Math.max(...array);

// standard loop
let max = testArray[0];
for (let i = 1; i < testArrayLength; ++i) {
  if (testArray[i] > max) {
    max = testArray[i];
  }
}

// reduce
const array = [{name: "a", value: 1}, {nama: "b", value: 2}]
array.reduce((a, b) => Math.max(a.value, b.value));

const array = [1,2,3,5,1,2]
array.reduce((a, b) => Math.max(a, b));

Time cost: standard loop < ES6 spread and apply < reduce

Finding the max value of an attribute in an array of objects

// reduce
const array = [{name: "a", value: 1}, {nama: "b", value: 2}]
const maxValueObject = array.reduce((prev, current) => (prev.value > current.value) ? prev : current)

Convert type of elements of Array

int array to string array

// This will not mutate array. It will return a new array.
let array = [1, 2, 3];
let newArray = array.map(String);

let array = [1, 2, 3];
let newArray = array.map(item => item.toString())

let array = [1, 2, 3];
let newArray = array.join(",").split(",");

string array to int array

// Note: For older browsers that don't support map
let array = ['1', '2', '3'];
let newArray = array.map(Number); // i=>Number(i)

let array = ['1', '2', '3'];
let newArray = array.map(item => parseInt(item));

let array = ['1', '2', '3'];
let newArray = Array.from(array, Number);

Request

URL Parameters

Getting URL parameters

// https://example.com/?id=1
const queryString = window.location.search;
console.log(queryString); // ?id=1
const urlParams = new URLSearchParams(queryString);
const id = urlParams.get('id');
console.log(id); // 1

Checking for the Presence of a Parameter

console.log(urlParams.has('id')); // true

Getting All of a Parameter’s Values

console.log(urlParams.getAll('size'));
// [ 'm' ]

//Programmatically add a second size parameter.
urlParams.append('size', 'xl');

console.log(urlParams.getAll('size'));
// [ 'm', 'xl' ]

Iterating over Parameters

const
  keys = urlParams.keys(),
  values = urlParams.values(),
  entries = urlParams.entries();

for (const key of keys) console.log(key);
// product, color, newuser, size

for (const value of values) console.log(value);
// shirt, blue, , m

for(const entry of entries) {
  console.log(`${entry[0]}: ${entry[1]}`);
}

Document

Remove Elements

remove element by id

document.querySelector("#remove").remove();

remove elements by class name

function removeElementsByClass(className){
    const elements = document.getElementsByClassName(className);
    while(elements.length > 0){
        elements[0].parentNode.removeChild(elements[0]);
    }
}

const removeElementsByClass = (className) => document.querySelectorAll(className).forEach(el => el.remove());

Empty Elements

empty element by id

document.querySelector("#remove").innerHTML = "";

empty elements by class name

const emptyElementsByClass = (className) => document.querySelectorAll(className).forEach(el => el.innerHTML = "");

Regular Expression

RegExp

// creating regular expression from a string, you have to double-up your backslashes \\.
const regex = new RegExp('^\\d{10}$');
const regex = new RegExp('^\\d{10}$', 'g');

/regex/mod

// if you use regex syntax, you need eacape / by \/
const regex = /^\d{10}$/;
const regex = /^\d{10}$/g;

API

• RegExp

  • regexp.exec(str) - Returns the first match info array. It likes [matched string, group 1, group 2, ...]. The flag g has no effect.

    /hello(\d)/.exec("hello1, hello2"); // ['hello1', '1', ...] /hello(\d)/g.exec("hello1, hello2"); // ['hello1', '1', ...]

  • regexp.test(str) - Returns whether it matches. The flag g has no effect.

    /hello(\d)/.test("hello1, hello2"); // true /hello(\d)/g.test("hello1, hello2"); // true

• String

  • string.match(regexp) - Returns the first match info array [matched string, group 1, group 2, ...], or return an all matched string array [matched string 1, matched string 2, ...] when it uses the flag g.

    let s = "hello1, hello2"; s.match(/hello(\d)/); // return the first match object ['hello1', '1', ...] s.match(/hello(\d)/g); // return all match strings ['hello1', 'hello2']

  • string.matchAll(regexp) - Returns all match info arrays. The regexp must use the flag g (global search).

    let s = "hello1, hello2"; s.matchAll(/hello(\d)/); // Uncaught TypeError: String.prototype.matchAll called with a non-global RegExp argument for (const match of s.matchAll(/hello(\d)/g)) { console.log(match); // the match info array console.log(match[0]); // the matched string console.log(match[1]); // the group 1 of the matched string }

  • string.replace(regexp, replacement) - Returns a string with the first or all matched string replaced.

    let s = "hello1, hello2"; s.replace(/hello(\d)/, 'hey'); // 'hey, hello2' s.replace(/hello(\d)/g, 'hey'); // 'hey, hey'

    // replace with group let s = "hello1, hello2"; s.replace(/hello(\d)/, "hi$1"); // 'hi1, hello2' s.replace(/hello(\d)/g, "hi$1"); // 'hi1, hi2' // extract group s.replace(/hello(\d)/g, "$1"); // '1, 2'

  • string.replaceAll(regexp, replacement) - Returns a string with the all matched string replaced. The regexp must use the flag g (global search).

    let s = "hello1, hello2"; s.replaceAll(/hello(\d)/, 'hey'); // Uncaught TypeError: String.prototype.replaceAll called with a non-global RegExp argument s.replaceAll(/hello(\d)/g, 'hey'); // 'hey, hey'

    // replace with group. // replaceAll(/xxx/g, '') results are same with replace(/xxx/g, '') s.replaceAll(/hello(\d)/g, "hi$1"); // 'hi1, hi2' s.replaceAll(/hello(\d)/g, "$1"); // '1, 2'

  • string.search(regexp)

  • string.split(regexp)

Flags

Match emoji unicode

const text = "Hello, 😀🚀🌎!";
const emojiRegex = /\p{Emoji}/gu;
const emojis = text.match(emojiRegex);

console.log(emojis); // ['😀', '🚀', '🌎']

Make sure to use the u flag at the end of the regex pattern (/.../u) to enable Unicode mode, which is necessary when working with Unicode property escapes.

References

• JavaScript data types and data structures
• Quick Tip: Get URL Parameters with JavaScript
• JavaScript: The Definitive Guide Content
• Regular expressions - MDN

Single sign-on (SSO) is an authentication method that allows users to sign in using one set of credentials to multiple independent software systems.

Implementations of single sign-on:

• Cookie-based
• Session-based
• Central Authentication Service (CAS)

Cookie-Based SSO

It works by using web based HTTP cookies to transport user credentials from browser to server without from the user. Credentials on the client machine are gathered and encrypted before it being stored in the cookie.

Once the user enters the username and password in any subsystem, the user credentials will be stored in cookie, which is shared by multiple subsystems and automatically sent to the server.

The domain name of each system using cookie-based SSO should be the same or have the same top-level domain name. So user credentials in cookie can be shared between multiple systems.

Advantages

• Easy to implement.

Disadvantages

• Can’t cross domain.

Session-Based SSO

It works by using web based HTTP cookies to transport user authentication token.

The user token is stored in the client browser and sent to the server as session value. session values and user ID are stored in a cache like Redis shared across subsystems. Each subsystem checks the user from the cache by the token in the HTTP request cookie.

Advantages

• Suitable for distributed system applications.

Disadvantages

• Can’t cross domain.

Central Authentication Service (CAS)

When the user accesses the application system for the first time, since he has not logged in, he is directed to the authentication system to log in. The authentication system accepts security information such as user name and password, and generates an access token (ticket). The user accesses the application system through the ticket. After receiving the request, the application system will visit the authentication system to check the legitimacy of the ticket. If the check is passed, the user can access the application system resources without logging in again.

Advantages

• Support cross domain.

Disadvantages

• Need a an independent authentication system.

Expressions

Divisor is zero

Exception:

java.lang.ArithmeticException

Error code example:

int a = 1;
int b = 0;
int result = a / b;

Suggestion:

You need to check if the divisor is zero.

Statements

Update a collection in for loop (Fail fast)

Exception:

java.lang.UnsupportedOperationException

Error code example:

List<Integer> list = Arrays.asList(1, 2, 3, 4, 5, 6);
for (int i = 0; i < list.size(); i++) {
    Integer value = list.get(i);
    System.out.println(value);
    if (value == 1) {
        list.add(100); // or list.remove(0);
    }
}

Suggestion:

Do not insert, update, and delete elements of a collection while looping through the collection.

Objects and Classes

Call a null object methods

Exception:

java.lang.NullPointerException

Error code example:

User user = null;
String name = user.getName();

Suggestion:

You need to check if the object is null when calling its methods.

Collections

Add elements to Collections.emptyList()

Exception:

java.lang.UnsupportedOperationException

Error code example:

List<Integer> list = Collections.emptyList();
list.add(1);

Suggestion:

Don’t return Collections.emptyList() in intermediate methods.

Add elements to List built by Arrays.asList()

Exception:

java.lang.UnsupportedOperationException

Error code example:

List<Integer> list = Arrays.asList(1, 2, 3);
list.add(4);

Suggestion:

If you need update the list later, you should use new ArrayList(Arrays.asList()) instead of Arrays.asList().

Requirement drives technology capabilities.

Keep Coding

Solve algorithm problems.

Do some great open-source projects (making wheels or writing common systems). Or contribute to open-source projects.

Keep Learning

Reading technical books and docs.

Writing blogs.

Creating some small toy projects.

Solving other code problems. Answer questions on StackOverflow.

Answer interview questions by yourself.

Browse technical websites and forums.

Deep Dive

Reading classic fundamental CS books, documentation, and specification.

Reading source code.

Naming Convention

Java uses camelCase as the naming convention for variables, methods, and classes. But class names must be capitalized.

Package management

You can use Maven or Gradle for package (dependency) management.

Project Creation

Maven project

You can create a Maven project in the following way.

1. Maven command line

$ mvn archetype:generate \
    -DgroupId=com.taogen.demo \
    -DartifactId={project-name} \
    -DarchetypeArtifactId=maven-archetype-quickstart \
    -DarchetypeVersion=1.4 \
    -DinteractiveMode=false

2. Create a Maven project in a IDE

3. Spring Initializr

Project structure

Basic Maven Application

java-project/
│
├── src/main/java/
│   └── com/taogen/javaproject/
│
├── src/main/resources/
│
├── src/test/java/
├── src/test/resources/
└── pom.xml

• src/main/java: Java source code
  • com/taogen/javaproject: Base package path. It represents the domain name of your project website.
• src/main/resources/: Static resources such as image, JavaScript, and CSS files. And configuration files.
• src/test/java/: Test code.
• pom.xml: Maven project configuration file.

Spring boot Web Application

java-project/
│
├── src/main/java/
│   └── com/taogen/javaproject/
│       ├── modules/
│       │   └── user/
│       │       ├── controller/
│       │       │      └── UserController.java
│       │       ├── entity/ (or domain/)
│       │       │      └── User.java
│       │       ├── service/
│       │       │      ├── UserService.java
│       │       │      └── impl/
│       │       │             └── UserServiceImpl.java
│       │       ├── repository/ (or mapper/)
│       │       │      └── UserRepository.java
│       │       ├── vo/
│       │       └── dto/
│       ├── util/
│       ├── config/
│       ├── aspect/
│       ├── annotation/
│       ├── constant/
│       ├── enums/
│       ├── exception/
│       ├── filter/
│       └── task/
│
├── src/main/resources/
│   ├── static/
│   ├── templates/
│   ├── log4j2.xml
│   └── application.yml (or application.properties)
│
├── src/test/java/
├── src/test/resources/
│
├── .gitignore
├── .gitmessage
├── Dockerfile
├── pom.xml
├── LICENSE
└── README.md

• src/main/java: Java source code
  • modules/
    • controller/: HTTP request handlers.
    • entity/: JavaBeans, POJOs, or domain models.
    • service/: Business logic processing code.
    • repository/: Data access layer code for various persistence stores.
    • dto/: Data Transfer Objects, encapsulate values to carry data between processes or networks.
    • vo/: Value objects, a special type of objects that can hold values.
  • util/: Utility classes such as StringUtil, DateUtil, IOUtil, etc.
  • config/: Configuration files such as Redis, MySQL data source, Security, etc.
  • aspect/: Spring AOP classes.
  • annotation/: Custom Java annotations.
  • constant/: Static variable classes.
  • enums/: Java Enum type classes.
  • exception/: Custom exception classes that are extended by a java.lang.Exception class or its subclass.
  • filter/: Servlet filter classes that are implemented javax.servlet.Filter.
  • task/: Scheduled tasks.
• src/main/resources/
  • static/: Static files such as CSS, JavaScript, image, etc.
  • templates/: Template files such as JSP, FreeMarker, Thymeleaf, etc.
  • log4j2.xml: Log configuration file.
  • application.yml: Spring boot configuration file.
• src/test/java/: Test code.
• pom.xml: Maven project configuration file.

Solve coding problems

Programming language coding problems

Solve problems on LeetCode

Do small toy projects

To-do list

Calculator

Snake game

Make projects that solve your own problems or requirements

Web page crawlers

Web video downloader

Automation scripts or tools

Contribute to open-source projects

You can search “How to find open source projects to contribute”

Create your own open-source project

Doing open source projects forces you to write better and clean code.

Getting Started

Introduction to the programming language

Programming environment

Print “Hello world”

An example of the combination of variables, functions, expressions, statements, standard Input, and output

Comment. Single line and multiline comments.

Variables and Data Types

Variables

Variable declaration, initialization, assignment.

Variable scope. Local variables and global variables.

Data Types

Data type table by categories

Data type literal (type initialization) examples

Get the type of the variable

Type check

Check null or undefined

Check string type

Check number type

Check object type

Check array type

Check function type

Type conversion

Conversion between bool, integer, float, and string

number to string

string to number

string to float

Type formatting

String formatting. placeholders formatting.

Integer formatting. Add leading zero. Specify length.

Float formatting. fixed-point decimal formatting.

Date formatting. Format date objects by pattern.

String and Array

String

String basic

String declaration and initialization. multiline strings.

Length of string

Lookup

chatAt. the n character of the string

indexOf, lastIndexOf

String check

equals

isEmpty

contains

startsWith, endsWith

matches regex

String conversion

toCharArray

toLowerCase, toUpperCase

String Handling

String concatenation

Substring

replace

trim

split

join

String formatting

Array / List

Array basic

Array declaration and initialization

length of array

Lookup

Access element by index

indexOf

contains

Operations

insert, append

update

remove

Handling

Deep copy

Slice or subarray

Array concatenation

Filter / Map / Reduce (sum, min, max) / Predicate (some, every)

Join

Sorting

Reversion

Deduplication

Conversion

Array to string

Expressions

Arithmetic operators

addition +, subtraction -, multiplication *, division /, remainder/modulo %, exponentiation ^.

Logical operators

and &&, or ||, not !

Comparison operators

equality ==, inequality !=, greater than >, less than <, >=, <=

Bitwise operators

bitwise AND &, bitwise OR |, bitwise NOT ~, bitwise XOR ^, left shift <<, right shift >>

Others operators

Assignment, member access, conditional operator

Operator precedence

Statements

Conditional

if

switch

For loop

while

for

do…while

Exception handling

try…catch…finally

throw

Functions

Function definition

Function call

Argument passing and return value

Modules

Classes and Objects

Object-Oriented Programming

Classes

Class definition

Class members. Constructors. Static and instance members of classes.

Objects

Object construction

Object Deep copy

Inheritance

Standard Library

I/O Streams and Files

Input/Output streams

Input stream types. Bytes input streams, character input streams, buffered input streams.

Output stream types. Bytes output streams, character output streams, buffered output streams.

Read from and write into files.

Read from and write into memory.

Read a text file as string

Non-blocking and asynchronous I/O

Moving data into and out of buffers

Files

File and directory operations. creation, delete, update.

File path.

File information. Mine type of files.

Temporary files and directories.

Container

Container types

List, Set, Map, Queue, Stack

Container Operations

Basic operations

Traversal, print, add elements, remove elements

Conversion

Element type conversion, Container conversion.

Common operations

Merge

Join

Deduplication

Sorting

Reversion

Computation

Reduction

Aggregation and group

Concurrent Containers

Thread and concurrency

Processes and threads

Synchronization.

Liveness. Deadlock and livelock (starvation).

Guarded blocks. wait and notifiy.

Immutable objects. Its state cannot change after it is constructed.

High level concurrency objects. Reentrant lock. Executors and thread pools. Concurrent collections. Atomic variables.

Network programming

Sockets

Web Sockets

Server-sent events

HTTP

HTTP clients.

Download files by HTTP URLs.

Security

Class loaders

User authentication

Digital signatures

Encryption

Advanced Topics

Lambda expressions and Functional Programming

Streams

Stream Creation

The filter, map Methods

Collecting Results

Grouping and Partitioning

Reduction Operations

Parallel Streams

Annotation

Generics

Reflection

Packaging and deployment

Regular expressions

Others

Package manager and create project.

Style Guide

Project structures.

Best practice.

Common libraries

• String handling
• DateTime handling

References

[1] What are the basic fundamental concepts of programming?

[2] C++ Primer, Fifth Edition - Table of Contents

[3] Java SE 8 API

[4] The Java Tutorial: A Short Course on the Basics - Table of Contents

[5] Core Java, Volume I: Fundamentals, 12th Edition - Table of Contents

[6] Core Java, Vol. II-Advanced Features, 12th Edition - Table of Contents

Factors in choosing a programming language

• Purpose
• Speed to Market / Productivity
• Popularity: Technology ecology
• Usability: Readable code, less effort
• Learning Curve / Simplicity
• Performance / Speed
• Security

Programming languages for developing web applications

When you’re talking about web applications at large scale, you have to consider things like security, performance, concurrency, developer productivity, scalability as a language, interoperability

Server-side programming languages for web application development

• Small scale project: PHP, Python, Ruby
• Large scale project: Java, Go, C# (.NET)
• Others: Node.js

Comparison table of web application server-side programming languages

PHP disadvantages

• Website may be difficult for modify if you don’t have a good architecture at the beginning.

Ruby disadvantages

• There is so many magic here makes you feeling very well at the beginning. But when you need to go deeper into the framework. There would be a lot of pain.

Programming languages for developing mobile applications

Android

The majority of Android apps are written in Java and Kotlin. In some cases, programming languages like C, C++, and Basic are also used.

Java

Kotlin

C/C++ (Android Native Development Kit (NDK))

• C++ can be used in Android app development in rare cases, especially when you plan to build native-activity Android applications. It is because C++ is less flexible and very difficult to set up, and as a result, it can lead to more bugs. Usually, Java is preferred more over C++.
• Google offers the native development kit (NDK) that uses native languages like C and C++ for Android development. But you can’t build an entire Android app with C or C++. You need to learn Java.

iOS

Swift

Objective C

Cross-Platform Mobile

C# (Xamarin)

Dart (Flutter)

Lua (Corona, Solar2D)

JavaScript (React Native)

Python (convert Python apps into Android Packages)

Programming languages for developing desktop applications

Windows

C, C++

C#(.Net)

Linux

C/C++

Mac OS X

Swift

Objective C

Cross-Platform Desktop

Java

Python

JavaScript (Electron)