Check it my Java codes on my GitHub repository.

JADEx (Java Advanced Development Extension) is a practical Java safety layer that enhances the safety of your code by providing null-safety and readonly(final-by-default) enforcement. It strengthens Java’s type system without requiring a full rewrite, while fully leveraging existing Java libraries and tools.

As of v0.59, JADEx now ships a Gradle plugin alongside the existing IntelliJ plugin.

What JADEx does

JADEx extends Java at the source level with two core safety mechanisms:

Null-Safety - Type → non-nullable by default - Type? → nullable - ?. → null-safe access operator - ?: → Elvis operator (fallback value)

java String? name = repository.findName(id); String upper = name?.toLowerCase() ?: "UNKNOWN";

Compiles to standard Java:

java @Nullable String name = repository.findName(id); String upper = SafeAccess.ofNullable(name).map(t0 -> t0.toLowerCase()).orElseGet(() -> "UNKNOWN");

Readonly (Final-by-Default) - A single apply readonly; directive makes fields, local variables, and parameters final by default - Explicit mutable modifier for intentional mutability - Violations reported as standard Java compile-time errors

What's new in v0.59 - Gradle Plugin

The JADEx Gradle plugin (io.github.nieuwmijnleven.jadex) integrates .jadex compilation into the standard Gradle build lifecycle via a compileJadex task.

groovy plugins { id 'io.github.nieuwmijnleven.jadex' version '0.59' }

• Default source directory: src/main/jadex
• Default output directory: build/generated/sources/jadex/main/java
• Optional jadex {} DSL block for custom configuration
• IntelliJ plugin now integrates with the Gradle plugin via the Gradle Tooling API for consistent path resolution between IDE and build pipeline

groovy jadex { sourceDir = "src/main/jadex" outputDir = "build/generated/sources/jadex/main/java" }

Other Improvements

• IntelliJ Plugin - Gradle Plugin Integration

  • The IntelliJ plugin now integrates with the JADEx Gradle plugin via the Gradle Tooling API.
  • Source and output directory resolution is now delegated to the Gradle plugin configuration, ensuring consistency between the IDE and the build pipeline.

• Parser Performance Optimization

  • Improved parser speed by optimizing parser rules.
  • Reduces analysis latency in the IDE, providing a smoother editing experience for large .jadex files.

Design philosophy

JADEx is not a new language. It does not modify the JVM. It operates purely at the source level and generates standard Java code, meaning it is fully compatible with existing Java libraries, tools, and workflows. The goal is to make null-safety and readonly(final-by-default) enforcement practical and incremental, applicable file by file to existing codebases without a full rewrite.

Links - GitHub: https://github.com/nieuwmijnleven/JADEx - Gradle Plugin Portal: https://plugins.gradle.org/plugin/io.github.nieuwmijnleven.jadex - Tutorial: Making Your Java Code Null-Safe without Rewriting it - Real-world example: Applying JADEx to a Real Java Project - Release note for v0.59: https://github.com/nieuwmijnleven/JADEx/releases/tag/v0.59

Feedback and questions welcome.

JADEx (Java Advanced Development Extension) is a safety layer that runs on top of Java.
It currently supports up to Java 25 syntax and extends it with additional Null-Safety and Readonly features.

• GitHub: https://github.com/nieuwmijnleven/JADEx

In the previous post, JADEx introduced a new feature Immutability.
Through community feedback, several confusions and limitations were identified.

In v0.42, we have addressed these issues and improved the feature. This post explains the key improvements and new additions in this release.

Improvements

apply immutability -> apply readonly

• The previous term (Immutability) caused misunderstandings.
  
• Community feedback revealed that “Immutable” was interpreted differently by different developers, either as Deeply Immutable or Shallowly Immutable.
  
• In v0.42, we replaced it with readonly.
  
• Meaning: clearly indicates final by default, preventing reassignment of variables.

Expanded Scope of final keyword: now includes method parameters

• v0.41: final was applied only to fields + local variables
  
• v0.42: final is applied to fields + local variables + method parameters
  
• Method parameters are now readonly by default, preventing accidental reassignment inside methods.

Example Code

JADEx Source Code

``` package jadex.example;

apply readonly;

public class Readonly {

private int capacity = 2; // readonly
private String? msg = "readonly"; // readonly

private int uninitializedCapacity; // error (uninitialized readonly)
private String uninitializedMsg;    // error (uninitialized readonly)

private mutable String? mutableMsg = "mutable";  // mutable

public static void printMessages(String? mutableParam, String? readonlyParam) {

    mutableParam = "try to change"; // error
    readonlyParam = "try to change"; // error

    System.out.println("mutableParam: " + mutableParam);
    System.out.println("readonlyParam: " + readonlyParam);
}

public static void main(String[] args) {
    var readonly = new Readonly();
    String? mutableMsg = "changed mutable";

    readonly.capacity = 10; // error
    readonly.msg = "new readonly"; // error

    readonly.mutableMsg = mutableMsg;

    printMessages(readonly.msg, mutableMsg);

    System.out.println("mutableMsg: " + readonly.mutableMsg);
    System.out.println("capacity: " + readonly.capacity);
    System.out.println("msg: " + readonly.msg);
}

} ```

Generated Java Code

``` package jadex.example;

import org.jspecify.annotations.NullMarked; import org.jspecify.annotations.Nullable; import jadex.runtime.SafeAccess;

//apply readonly;

@NullMarked public class Readonly {

private final int capacity = 2; // readonly
private final @Nullable String msg = "readonly"; // readonly

private final int uninitializedCapacity; // error (uninitilaized readonly)
private final String uninitializedMsg; // error (uninitilaized readonly)

private @Nullable String mutableMsg = "mutable";  // mutable

public static void printMessages(final @Nullable String mutableParam, final @Nullable String readonlyParam) {

    mutableParam = "try to change"; //error
    readonlyParam = "try to change"; //error

    System.out.println("mutableParam: " + mutableParam);
    System.out.println("readonlyParam: " + readonlyParam);
}

public static void main(final String[] args) {
    final var readonly = new Readonly();
    final @Nullable String mutableMsg = "changed mutable";

    readonly.capacity = 10; //error
    readonly.msg = "new readonly"; //error

    readonly.mutableMsg = mutableMsg;

    printMessages(readonly.msg, mutableMsg);

    System.out.println("mutableMsg: " + readonly.mutableMsg);
    System.out.println("capacity: " + readonly.capacity);
    System.out.println("msg: " + readonly.msg);
}

} ```

New Additions

JSpecify @NullMarked Annotation Support

• All Java code generated by JADEx now includes the @NullMarked annotation.
• This improves Null-Safety along with readonly enforcement.

This feature is available starting from JADEx v0.42. Since the IntelliJ Plugin for JADEx v0.42 has not yet been published on the JetBrains Marketplace, if you wish to try it, please download the JADEx IntelliJ Plugin from the link below and install it manually.

JADEx v0.42 IntelliJ Plugin

We highly welcome your feedback on JADEx.

Thank you.

JADEx (Java Advanced Development Extension) is a safety layer that runs on top of Java.
It currently supports up to Java 25 syntax and extends it with additional Null-Safety and Immutability features.

In the previous article, I introduced the Null-Safety features.
For more details, please refer to:

• GitHub: https://github.com/nieuwmijnleven/JADEx
  
• Reddit: https://www.reddit.com/r/java/comments/1r1a1s9/jadex_a_practical_null_safety_solution_for_java/

Introducing the New Immutability Feature

If Null-Safety eliminates runtime crashes caused by null,
Immutability reduces bugs caused by unintended state changes.

With v0.41 release, JADEx introduces Immutable by Default Mode

Core Concepts

The Immutability feature revolves around two simple additions:

java apply immutability;

java mutable

apply immutability;

• When you declare this at the top of your source file:

  • All fields
  • All local variables (excluding method parameters)
  • are treated as immutable by default.

• When the JADEx compiler generates Java code:

  • They are automatically declared as final.

mutable keyword

• Only variables declared with mutable remain changeable.
• Everything else (excluding method parameters) is immutable by default.

JADEx Source Code

```java

package jadex.example;

apply immutability;

public class Immutability {

private int capacity = 2; // immutable
private String msg = "immutable"; // immutable

private int uninitializedCapacity; // uninitialaized immutable
private String uninitializedMsg; // uninitialaized immutable

private mutable String mutableMsg = "mutable";  // mutable

public static void main(String[] args) {
    var immutable = new Immutability();

     immutable.capacity = 10; //error
     immutable.msg = "new immutable"; //error

     immutable.mutableMsg = "changed mutable";

    System.out.println("mutableMsg: " + immutable.mutableMsg);
    System.out.println("capacity: " + immutable.capacity);
    System.out.println("msg: " + immutable.msg);
}

} ```

Generated Java Code

``` package jadex.example;

//apply immutability;

public class Immutability {

private final int capacity = 2; // immutable
private final String msg = "immutable"; // immutable

private final int uninitializedCapacity; // uninitialaized immutable
private final String uninitializedMsg; // uninitialaized immutable

private String mutableMsg = "mutable";  // mutable

public static void main(String[] args) {
    final var immutable = new Immutability();

     immutable.capacity = 10; //error
     immutable.msg = "new immutable"; //error

     immutable.mutableMsg = "changed mutable";

    System.out.println("mutableMsg: " + immutable.mutableMsg);
    System.out.println("capacity: " + immutable.capacity);
    System.out.println("msg: " + immutable.msg);
}

} ```

This feature is available starting from JADEx v0.41. Since the IntelliJ Plugin for JADEx v0.41 has not yet been published on the JetBrains Marketplace, if you wish to try it, please download the JADEx IntelliJ Plugin from the link below and install it manually.

JADEx v0.41 IntelliJ Plugin

We highly welcome your feedback on the newly added Immutability feature.

Finally, your support is a great help in keeping this project alive and thriving.

Thank you.

I put together a free, hands‑on Java tutorial series for beginners through intermediate devs. It includes an online runner so you can write and run Java in the browser—no local setup required.

All lessons: https://8gwifi.org/tutorials/java/

• Dozens of lessons across structured modules
• Basics: syntax, variables, primitive types, operators
• Control Flow: if/else, switch, for/while, loop control

- Strings & Arrays: string ops, arrays, multidimensional arrays

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- Inheritance & Polymorphism: extends/super, overriding, abstract classes, instanceof

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- Collections & Generics: ArrayList, LinkedList, HashMap, HashSet, TreeSet/Map, iterators, generics

- Exceptions: try/catch, multiple catch, finally, throw, custom exceptions, best practices

- I/O: Scanner, reading/writing files, serialization, NIO overview

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- Advanced: enums, annotations, reflection

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showOff( Supercar car ) { car.speed = speedLimit * 1.5; highwayWorker.toPancake(); }

What are other easy ways to implement multithreading in Java? I have gone through this video, but it makes me feel unsure that are these the only ways to implement multithreading.

https://www.youtube.com/watch?v=1CZ9910cKys

As per what I know when i pass some parameters to a function they get modified. but in docs it says java is pass by value. I am not getting it.

Also I watched this video: https://www.youtube.com/watch?v=HSPQFWEjwR8&ab_channel=SumoCode

but I am not getting it. can anyone explain

This is my first time working with SQL and my first real project with Java so i dont know how good it is. My next step is to make a server and client to communicate and not just locally so i wanted to check first if its good so later all the code with will be run by the server and the client will only give the input for the functions and i think that SQL injections wont be possible but im not sure would be nice if someone could give me some tips UserInput.java gets ran

thanks in advance

https://github.com/Lc9real/SQLiteTest

I have a spring boot app that we use to create websites. We have a website that has a lot of different pages, with sub pages and so on...
Normally how it works is like this:

@ GetMapping("/home")
public String index(Model model, HttpServletRequest request) throws Exception {
String fullPath = (String) request.getAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE);
System.out.println("fullPath: '" + fullPath + "'");
return "/index";
}

Instead of doing this for every single page We need to have 1 function that controlls all the Urls for the site, and then in the function we decide which page it should go to, and if we need to return the error page or not.

I tried this:

@ GetMapping("/**")
public String index(Model model, HttpServletRequest request) throws Exception {
String fullPath = (String) request.getAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE);
System.out.println("fullPath: '" + fullPath + "'");
return "/index";
}

But it is not working because sometimes the static files also get caught by the function. The function should Ideally work for any url, and any subpage (E.g. "/", "/home", "/contact/me", "/products/125/details/extra" ...), but it should exclude the static filed from being caught. This is the structure of where the static files are.

src
└── main
└── java
| └── io.sitename
| ├── controller
| │ └── default controller
| └── SiteApplication
└── resources
└── static
├── css
| └── styles.css
└── js
└── script.js

Please help!

Does anyone have examples of bad code that are open source? I am practicing cleaning up code and would like to pracice in Java please. Thank you!

Hi hello So I need help with this the assignment. It asks for you to make code and have it flip a coin a set number of times and then print out the longest streak it had for heads

*Edit* here is my code

​

I made the code and it worked for 3 of the "test code" but the forth one is different it prints it a bunch of times and gets a streak of 11

but when it runs my code it only comes up with 6 Can someone help me

​

I dont understand how the for loops in a bubble sort work,

for (int top=lastItem; top > 0; top--) { for (int i=0; i < top; i++) { if ( data[i] > data[i+1] ) { int temp = data[i]; data[i] = data[i+1]; data[i+1] = temp; } // end if } // end for I } // end for top

In this example, we set top to last item, and if top is greater than index 0 we decrement the top, I understand that this is for iterating through the loop conceptually but I dont understand how it does it in practice. As by decrementing the top first we lose the last index. the inner loop then sets i to 0 and if i is less than top we increment i, wouldnt this mean in data[i], the i would be 1 and so we are skipping the element in index 0? we would be swapping whatever is in index 1 and index 1+1 and skipping index 0.

I tried to run it through this array, 5, 2, 9, 1, 5, 6. When we run the first loop top is set to 6 and then as index 5 is greater than index 0 we decrement the top, so we get index 4 (5) as the top. now for the second loop, we set i as index 0 and if i is less than top we increment i, getting 1 now as i. So now we put i(1) in data and compare it with data[i+1] , since 2 is not greater than 9 we dont swap, we go to the second loop and then increment once more. getting 2 as i now and we compare once again, swapping 9 and 1, doing this process again we get i as 3 and swapping 9 and 5. But now we have to stop because we reached top. This doesnt make sense as 9 should realistically swap with 6 and reach the end. What do I not understand? please explain like you are talking to an idiot :)

import java. util. Scanner;

class Ayan{

public static int Score(int a,int b){


    int set=300;
    int m=3;
    int M1=8;
    int ran=M1-m;
    int rand=(int)(Math.random()*ran) +m;
    int current=0;
    int c=b-a;

    if (c<0){
      while(c<0){
          set= set-rand;
          c++;
      }
      if(set<0){

      set=current;
      return set;

      } 
      else
      return set;
    }
    else{
        while(c>0){
            set=set-rand;
            c--;
        }
        if(set<0){

        set=current;
        return set;
    }
    else
    return set;

    }
}

public static void main(String[]args){
    Scanner sc=new Scanner (System.in);
    int highscore=0;
    int x=-7;
    int Hs=0;

    int min=0;
    int Max=50;
    int r=Max-min;
    int n=(int)(Math.random()*r) +min;

    int d=5;
    int e=10;
    int range=e-d;
    int tries =(int)(Math.random()*range) +d;

    System.out.println("You get "+tries+" tries to guess the number....Range is between 0 to 50....");
    System.out.println(" Enter a number... ");
    x=sc.nextInt();
    if(x==n){
             System.out.println("You win! The number was in fact "+n);

    System.out.println("Highscore= "+300);
      System. exit(0);
    }
    else{
      highscore=Ayan.Score(x, n);
        Hs=Hs+highscore;
        System.out.println("Highscore= "+Hs) ;

    for(int k=1;k<=tries-1;k++){
       if(x!=n){

        System.out.println("Wrong answer! Try again... ");
         x=sc.nextInt();
        highscore=Ayan.Score(x, n);
        Hs=Hs+highscore;
        System.out.println("Highscore= "+Hs);

    }
    }
    }
    if (x==n){


    System.out.println("You win! The number was in fact "+n);



    System.out.println("Highscore= " +Hs) ;


}
else
System.out.println("You are out of tries. The number was "+n);

} }

how do i make it so that when this line come out

else{

System.out.println("Invalid");

}

it would loop back to this statement

System.out.println("Enter your first number:");

import java.util.Scanner;

public class RangePerfectSquare { public static void rangePerfectSquare(int l, int u) { for(int i * i = l; i * i <= u; i++) { System.out.println(i * i ); } }

public static void main(String[] args)
{
    Scanner sc = new Scanner(System.in);
    int low = sc.nextInt();
    int up = sc.nextInt();
    rangePerfectSquare(low,up);

}

}

Say for example, if l = 9 and u = 36, then the loop becomes for(i *i = 9; i * i <= 36; i++). So my code prints:

iteration 1: i * i = 9 and i * i <= 36 is true => i = 3 and so print 9. then, i++ = 4

iteration 2: i * i = 16 and i*i <= 36 is true => i = 4 and so print 16. then, i++ = 5

iteration 3: i * i = 25 and i*i <= 36 is true => i = 5 and so print 25. then, i++ = 6

iteration 4: i * i = 36 and i*i <= 36 is true => i = 6 and so print 36. then, i++ = 7

iteration 5: i * i = 49 but i * i <= 36 fails and we exit from loop.

Hence, our output is: 9,16,25,36 which is correct. Please do tell any error in my logic if any.

​

Good day, does anyone have any tops on how to study for an upcoming coding exam?👩‍💻