onixbyte-bom/devkit-utils

Module devkit-utils

Introduction

This module is part of JDevKit, an open-source Java Development Kit that provides a set of convenient tools to streamline code development and enhance productivity. This module serves as the useful toolkit for the library, contains a collection of utility classes commonly used in all Java Application development.

Prerequisites

This whole JDevKit is developed by JDK 17, which means you have to use JDK 17 for better experience.

Installation

If you are using Maven

It is quite simple to install this module by Maven. The only thing you need to do is find your pom.xml file in the project, then find the <dependencies> node in the <project> node, and add the following codes to <dependencies> node:

<dependency>
	<groupId>cn.org.codecrafters</groupId>
    <artifactId>devkit-utils</artifactId>
    <version>${devkit-utils.version}</version>
</dependency>

And run mvn dependency:get in your project root folder(i.e., if your pom.xml is located at /path/to/your/project/pom.xml, then your current work folder should be /path/to/your/project), then Maven will automatically download the jar archive from Maven Central Repository. This could be MUCH EASIER if you are using IDE(i.e., IntelliJ IDEA), the only thing you need to do is click the refresh button of Maven.

If you are restricted using the Internet, and have to make Maven offline, you could follow the following steps.

1. Download the jar file from any place you can get and transfer the jar files to your work computer.
2. Move the jar files to your local Maven Repository as the path of /path/to/maven_local_repo/cn/org/codecrafters/devkit-utils/.

If you are using Gradle

Add this module to your project with Gradle is much easier than doing so with Maven.

Find build.gradle in the needed project, and add the following code to the dependencies closure in the build script:

implementation 'cn.org.codecrafters:devkit-utils:${devkit-utils.version}'

If you are not using Maven or Gradle

1. Download the jar file from the Internet.
2. Create a folder in your project and name it as a name you like(i.e., for me, I prefer vendor).
3. Put the jar file to the folder you just created in Step 2.
4. Add this folder to your project classpath.

Base64 Encode and Decode

If you are trying to encode a string to Base64 string or decode a Base64 string to normal string, then you can try this:

import cn.org.codecrafters.devkit.utils.Base64Util;

// To reduce sample codes, let me use the simplified main method that is upcoming in Java 21
void main(String... args) {
    var aString = "The string you need to encode.";
    // Encode it from original text.
    var encodedString = Base64Util.encode(aString);
    // Decode the encoded text.
    var decodedString = Base64Util.decode(encodedString);
}

Reduce if...else...

I believe those if...else... blocks make you headache, and Java imported lambda since Java 8, why not try to replace those if...else with lambda expressions?

import cn.org.codecrafters.devkit.utils.BranchUtil;

void main(String... args) {
    var a = 1;
    var b = 2;
    
    if (a < b) {
        // do something...
    } else {
        // do something different...
    }
    // The codes above is really annoying, have a try of the lambda version.
    
    BranchUtil.or(a < b) // If multiple logical expressions are combined using the OR operator.
        .handle(() -> {
            // do something if a < b.
        }, () -> {
            // do something if a > b.
        });
    
    BranchUtil.and(a < b) // If multiple logical expressions are combined using the AND operator
        .handle(() -> {
            // do something if a < b.
        }, () -> {
            // do something if a > b.
        });
}

What if you have to get some data from this branch? Don't worry, those lambda supports Supplier. Just add a return in those lambda is fine.

CHAINED High-precision Calculation

If you have faced high-precision mathematical calculation in Java, you might know it is very troubled to do it in ANY programming languages. I'm certain you remember that 0.1 + 0.2 != 0.3 right?

In Java, we usually do high-precision mathematical calculation with BigDecimal which is quite tricky when using it.

import cn.org.codecrafters.devkit.utils.ChainedCalcUtil;

void main(String... args) {
    // If you are trying to calculate the expression of 1 * 2 / 2 - 3 + 4
    ChainedCalcUtil.startWith(1).multiply(2).divide(2).subtract(3).add(4).getInteger(); // you can also get a double by getDouble([int scale]), get a BigDecimal by getDecimal([int scale]) or get a long by getLong().
}

If you are facing a divide calculation which has an infinite decimal expansion, then DON'T use divide(dividend), use divideWithScale(dividend, scale, [beforeOperateScale]).

Hash a String

As is well known, storing plain text passwords in a database is very insecure. Therefore, you need to encrypt the passwords stored in the database, or at least make it difficult for hackers to see the real password at a glance. As a result, hash calculation is often used in database password obfuscation due to its ease of use.

This HashUtil supports these following hash or message digest algorithms:

• MD2
• MD5
• SHA-1
• SHA-224
• SHA-256
• SHA-384
• SHA-512

If you want to run a hash calculation to a string, you can use the following codes:

import cn.org.codecrafters.devkit.utils.HashUtil;

void main(String... args) {
    var plaintext = "This is a plain text";
    var hashedText = HashUtil.md2(plaintext); //  if you want to use other algorithm, just change the method name such as md5, sha1, sha224 and so on.
}

Besides, if you want to use other character set to do the hash calculation, you can add the specified charset after the text to be calculated.

HashUtil.$algorithm$(String textToCalculate, Charset charset);

Convert a Map to Any Object and Vice Versa

A Map is a data structure that allows you to store key-value pairs. The keys can be of any type and the values can be of any type. In this case, the key is the user's name and the value is the user's profile.

Imagine you are developing a website where users can register an account and store their profile. A profile can contain information like their name, age, address, and email address. You store the user's profile in a Map. When the user registers an account, you need to store their profile in a database. A database is a system for storing data. A database can store any type of data, including Maps.

In order to store the Map in a database, you need to convert the Map to an Object. An Object is a generic data type that can store any type of data.

import cn.org.codecrafters.devkit.utils.MapUtil;

class Data {
    private String name;
    private Long id;
    private Integer age;
    
    // Setters and getters here.
    
    // No-args constructor and all-args constructor here.
}

void main(String... args) {
    // Create a map.
    var dataMap = new HashMap<String, Object>();
    dataMap.put("name", "Zihlu Wang");
    dataMap.put("id", 1L);
    dataMap.put("age", 18);
    
    // Convert this map to an instance of class Data
    var data = MapUtil.mapToObject(dataMap, Data.class); // Then you got an instance of Data("Zihlu Wang", 1L, 18);
    
    // Then you can convert this object to a map.
    var anotherDataMap = MapUtil.objectToMap(data)
}

Contact

If you have any suggestions, ideas, don't hesitate contacting us via GitHub Issues or Discord Community.

If you face any bugs while using our library and you are able to fix any bugs in our library, we would be happy to accept pull requests from you on GitHub.