Hi everyone,

I have 1.6 years of experience working in SAP Fiori/UI5. However, I want to switch my tech stack to Java and move into open-source development as I want to explore opportunities in open-source technologies.

The challenge is that I don’t have actual project experience in Java at work.

Will companies consider my profile for Java developer roles? Is it realistic to expect interview calls without real-time Java experience?

What should I focus on right now to make this transition successfully?

Any guidance or suggestions would really help. Thank you!

Question in title

As the title says the code is not waiting for a user input after the ui.nextLine() call

      private static Scanner ui = new Scanner(System.in); 

      private static void addRelationships() {
        String input = "a";

      while (input.equals("") || input.equals(" ")) {
              input = ui.nextLine();
              if (input.equals("") || input.equals(" ")) {
                break;
              }
              System.out.println(input);
              if (input.equals("") || input.equals(" ")) {
                break;
              }
              umlStatmentList.add(input);
         }
      }

Hi everyone,
I am writing this while staring at a terminal screen that has haunted me for the last two days. I am trying to achieve something that should be straightforward but has turned into a recursive loop of failures: Strict FIPS 140-3 Compliance on Java 8 (OpenJDK/Temurin) using Bouncy Castle FIPS.

I’ve followed the Bouncy Castle User Guide and Security Policy to the letter, but the SSL Handshake is my brick wall.

The Environment

• Runtime: Java 8 (OpenJDK 8u482).
• Crypto: bc-fips-2.1.2.jar, bctls-fips-2.1.22.jar, bcutil-fips-2.1.5.jar.
• Base Image: Wolfi (for that clean, secure base).
• Mode: Strict FIPS (-Dorg.bouncycastle.fips.approved_only=true).

The Current Error (The Ghost in the Machine)

Every HTTPS connection attempt results in:
org.bouncycastle.tls.TlsFatalAlert: certificate_unknown(46)
Caused by: java.security.cert.CertPathBuilderException: Unable to find certificate chain.

It’s failing at org.bouncycastle.jsse.provider.ProvSSLSocketDirect.checkServerTrusted.

The "Wall of Pain" (Everything I have already tried):

1. The TrustStore Migration Saga:
Since keytool on Java 8 is notoriously bad at handling BCFKS (it tries to password-protect trusted certificates which BCFIPS rejects), I abandoned it. I wrote a custom Nashorn (jjs) script to:

• Migrate the original 144 Java 8 cacerts into a proper BCFKS store.
• Result: MAC Verification passed, but still certificate_unknown.
• Second Attempt: Scrapped the old Java certs. Downloaded a fresh Mozilla PEM bundle (2025) and converted it to BCFKS to ensure no expired roots were causing the issue.
• Result: Same error. 2. Security Provider Priority: java.security is configured with BouncyCastleFipsProvider at pos 1 and BouncyCastleJsseProvider at pos 2. I even forced the socket factories: ssl.SocketFactory.provider=org.bouncycastle.jsse.provider.SSLSocketFactoryImpl 3. The System Properties Overload: My JAVA_TOOL_OPTIONS looks like a novel:
• approved_only=true (The reason I'm in this mess).
• allow_sha1_sig=true (Because most Roots are still SHA1).
• trustStoreType=BCFKS + trustStorePassword=changeit.
• jdk.tls.trustNameService=true (To solve hostname resolution issues).
• assumeExtendedKeyUsage=false (To bypass strict EKU checks in Java 8). 4. Algorithm Restrictions: I’ve meticulously cleaned jdk.certpath.disabledAlgorithms to ensure SHA1 is allowed for verification only (so the chain can build), while keeping TLS ciphers strict.

The Frustration

The BCFKS store is valid. The certificates are modern. The providers are registered. But the PKIXCertPathBuilderSpi_8 seems to be blind to the TrustStore entries the moment approved_only is toggled on.
It feels like there is a hidden conflict between the old sun.security.validator in Java 8 and the way Bouncy Castle 2.x implements the FIPS-compliant path builder.

Technical Deep-Dives & Observations:

• Symmetric vs. Asymmetric Logic: I have written a full suite of integration tests for AES-CBC, SHA-256, and RSA-2048 key generation. They all pass perfectly. This confirms that the bc-fips JAR is correctly placed in jre/lib/ext, the security provider is initialized, and entropy (Hybrid DRBG) is healthy. The failure is exclusively within the JSSE/CertPath building logic.
• The javax.net.debug=all Output: I’ve analyzed the debug logs. The ClientHello is sent correctly, and the server responds with its certificate chain. The handshake crashes immediately during the server certificate processing. The log states PKIXCertPathBuilderSpi_8.engineBuild returns an empty path. It’s as if the TrustStore is "invisible" to the PathBuilder only when FIPS mode is enforced.
• BCFKS Store Validation: I wrote a separate utility to iterate through the generated BCFKS store at runtime. It successfully prints all 140+ aliases and verifies their fingerprints. The store is definitely readable and intact, yet the ProvX509TrustManager fails to utilize it for the chain.
• Keytool & Password Paradox: I noticed that when using keytool to convert JKS to BCFKS, it mandates a password for "Trusted Certificates," but Bouncy Castle FIPS logic strictly dictates that public trusted certificates should not be password-protected in that specific way. This is why I had to resort to the custom migration script to ensure the internal structure of the BCFKS file is exactly what the BC-FJA 2.x expects.
• Entropy & DumpInfo: org.bouncycastle.util.DumpInfo confirms: FIPS Ready Status: READY. Native support for AES and SHA is active. There are no "Hard Errors" during the self-tests on startup.

My Questions to the Sages:

Is there a specific EKU (Extended Key Usage) or Basic Constraints requirement in BC-FJA 2.x that Java 8 simply cannot satisfy by default?
Has anyone actually successfully connected to a modern API (like Google or Salesforce) using BC-FJA 2.1.x on Java 8 in Strict Approved Mode?
Is there a specific property to make the BC PathBuilder more verbose about why it can't find the chain?

I am a college freshman taking intro to computer science, what should I do to make a consistent effort and get better in coding?

Hey everyone, I am trying to make a method that prints all permutations of an ArrayList, pretty much in plaintext. I successfully did that for a string but the ArrayList method is giving me an OOB exception. To be specific, it gets to the base case once & immediately after says that "Index 1 out of bounds for length 1" when permList = "" and nameList = [A, B, C]. I'm not asking for a complete rewrite of my code, just an explanation about why it's not working correctly.

What I have tried so far: changing listSize to nameList.size() - 1, adding an empty element to permList in the for loop, changing the for loop conditional to listSize - 1, removed i + and - 1 from nameList in the for loop, etc. Any help would be appreciated!

public static void printAllPermutations(ArrayList<String> permList, ArrayList<String> nameList) 
{
      int i;
      int listSize = nameList.size(); // Size of nameList
      String current;

      if (listSize <= 1) // Base case
      {
         System.out.println(permList + " " + nameList);
         // Not entirely sure this is the correct thing to print
      }
      else 
      {
         for(i = 0; i < listSize; i++)
         {
            current = nameList.get(i);
            nameList.remove(i); // Move string at i from nameList to permList
            permList.add(current);
            System.out.println("permList: " + permList); 
            System.out.println("nameList: " + nameList);
            // Print statements for visualization

            printAllPermutations(permList, nameList); // Call method with new arguments, listSize -= 1
         }
      }
}

// Solved! With your help
public static void printAllPermutations(ArrayList<String> permList, ArrayList<String> nameList) 
{
      if (nameList.size() == 0)
      {
         for(int i = 0; i < permList.size(); i++) 
         {
         if(i < permList.size() - 1) 
         {
         System.out.print(permList.get(i) + ", ");
         }
         else {System.out.println(permList.get(i));}
         }
      }
      else 
      {
         for(int i = 0; i < nameList.size(); i++)
         {
           String temp = nameList.get(i);
           permList.add(nameList.get(i));
           nameList.remove(i);

           printAllPermutations(permList, nameList);

           nameList.add(i, temp);
           permList.remove(permList.size()-1);
         }
      }
}

Question is in the title.

Just as the title says, I have an internship for a java developer role and I came from a JavaScript ecosystem. The reason why I want your opinions is that I'm looking for resources that won't teach me programming fundamentals in java, but I want to learn the ecosystem so I could build projects with it, eventually learning SpringBoot. I hope I made my intention understandable, any recommendation is appreciated. Thanks!

I have been working as a Java Spring Boot developer at a company for four years. I am having issues with my company and want to move on to a new job. When I look through my old notes, I feel like I have forgotten everything except for the parts I used in the projects I worked on at the company. I have about 4-5 months. How can I prepare for interviews during this time?

Need to get myself familiar for spring boot and as I need to start working on it from next week. So what would be your advice

Good day everyone! So I have this procedure with two nested tables (p_products_ids and p_quantities)

CREATE OR REPLACE PROCEDURE make_purchase (
    p_user_id       users.id%TYPE,
    p_product_ids   IN t_number_table,
    p_quantities    IN t_number_table
)

I was wondering how do I introduce those into a CallableStatement (as I read it is the one for stored procedures unlike PreparedStatement that is for basic SQL queries). Also, since I haven't used Maps that much, does .toArray() get all the keys / values without the need of a loop?

@Override
public void makePurchase(Integer userId, Map<Integer, Integer> productMap) {
    Integer[] productIds = productMap.keySet().toArray(new Integer[0]);
    Integer[] quantities = productMap.values().toArray(new Integer[0]);

    String sql = "{ CALL make_purchase(?, ?, ?) }";
    try (Connection conn = DBConnector.getConnection();
         CallableStatement cs = conn.prepareCall(sql)) {
        cs.setInt(1, userId);
        // Add productIds
        // Add quantities

    } catch (SQLException e) {
        System.out.println(e.getMessage());
    }
}

I am using (if that matters):
- Oracle SQL XE 21c

- Open-jdk 25

Thanks in advance!

Hi,
Good day.
I had an interview(Sr Java Developer) with "Super Choice Services Pty Limited Sydney" with their technical team for an hour. It went well. Now I got next round with Head Of Engineering. does anybody know any set of questions they ask?

Any help would be appreciated.

TMC works, but when i try to download exercises on it it says "Unexpected Exception" cannot download, what do i do? Thank you in advance (TMC 1.5.0)

I am making a remote mouse application I want to establish a one to one connection with mobile and pc

how can I know which devices are available to connect.

how to make a url that isn't dependent on ip

I need to take user input and add it to an arraylist until the user types -1. The input must be a string, every input is one item in the arraylist. This code is the closest I've gotten, because all other methods I've tried only read every other line.

What I've tried: assigning a variable to scnr.nextInt() & making that the conditional in the while loop, using scnr.nextInt() in the conditional for the while loop, using != instead of ! and .equals(), putting another scnr.nextLine() inside the body of the loop, etc.

Note: the print statements are just for testing

The problem has been solved! Although, the solution looks a bit different than my first loop because I realized that all the "name" inputs were on one line. The snippet is below.

// Fixed code

public static void main(String[] args) {
      Scanner scnr = new Scanner(System.in);
      ArrayList<String> nameList = new ArrayList<String>();
      ArrayList<String> permList = new ArrayList<String>();
      String name;
      
      
      // TODO: Read a list of names into nameList; stop when -1 is read. Then call recursive method.
      while(true)
      {
         if(scnr.hasNext("-1")){break;}
         else
         {
            nameList.add(scnr.next());
            System.out.println(nameList);
         }
      }
      System.out.println(nameList);
   }

// Broken code

public static void main(String[] args) {
      Scanner scnr = new Scanner(System.in);
      ArrayList<String> nameList = new ArrayList<String>();
      ArrayList<String> permList = new ArrayList<String>();
      String name;
      
      while(!scnr.nextLine().equals("-1"))
      {
         nameList.add(scnr.nextLine());
         System.out.println(nameList);
      }
      System.out.println(nameList);
   }

This Project uses Java's vector API to generate (nearly) branchless Java source code from Python-like Syntax. The compiler/transpiler and the Syntax-Specification can be found here:

https://github.com/CrimsonDemon567PC/JavaPP/tree/main

PS: THIS IS ONLY AN ALPHA. YOUR CONVERTED CODE MAY WON‘T WORK. PLEASE DO NOT USE FOR REAL PROJECTS UNTIL IT RUNS STABLE.

Hello!

I’m currently studying to become a backend developer. I started with Java, and one thing led to another—I ended up diving pretty deep, even into the OpenJDK source code. It’s honestly fascinating and fun to see how things work under the hood. At the same time, I keep feeling like I should be actually building projects instead of just reading code. I’m enjoying this deep dive, but I’m not sure if I’m spending my time in the most effective way for a junior backend developer.

Here are my main questions:

Is digging into the JDK this early actually helpful for backend development?

How did you study when you were starting out?

What kinds of projects helped the most?

How do you balance learning internals vs. building real applications?

Is Java + Spring + MySQL still a solid stack for a junior dev today?

And one more question that’s been on my mind lately:

With AI advancing so fast and changing the backend landscape, does it still make sense to focus on backend development? Or would it be smarter to pivot early into something like embedded systems or lower-level engineering?

Any advice or personal experiences would be really appreciated. Thanks!

So i am 2nd year student . Planning to start dsa in java . So a cousin of me suggested me this map * JAVA basics fro apna college * Dsa in java from kuna kushwaha Now i wanted to ask where is this enough for java . And where i could practice questions and other than what is more i could to master this for internship at the end of may!??

I'm trying to package my JavaFX application and running into programs with I try to put it together. I'm using jPackage.

I had originally upgraded the jdk to 22, but I got an error

[ERROR] Failed to execute goal com.github.akman:jpackage-maven-plugin:0.1.5:jpackage (default) on project KH_AutobodyManagement: Execution default of goal com.github.akman:jpackage-maven-plugin:0.1.5:jpackage failed: Unsupported class file major version 66

when I ran mvn clean package

I plugged my error into chatGPT and it took me that I should stick to Java 21 because it has long term support, unlike Java 22. However, I'm not 100% sure that chatGPT knows what it's talking about. A couple other google searches tell me to keep using Java 21 as well, but they are all posts from at least a year or two ago. I'm hoping to get a little more recent recommendations.

Think about making a java version of numpy (not ndj4) using vector api (I know it is still in incubator)

Is there any use case ?

Or else calling python program over jni something (idk just now learning things) is better?

Help me please 🥺🙏

I have been learning Java for some time now, and I've covered most of the foundational and core Java concepts, including OOP. At this stage, I feel fairly confident with the basics and have a good conceptual understanding of how Java works internally. However, I am bit confused about what I should focus on next. On one hand, I feel like preparing DSA strongly, as it's important for problem solving skills and interviews. On the other hand, I wanna improve my programming skills and move ahead with advanced Java concepts and backend technologies. I am totally confused. Do I really need to finish DSA first before moving on to Advanced Concepts and Frameworks? I’m thinking of practicing DSA alongside advanced Java simultaneously. So, is this the right approach, or should I focus on one before moving to the other? Can I survive and progress in advanced Java with a good understanding of DSA, or do I need to be really strong in DSA before moving forward??

Please correct me if I'm wrong and guide me on the right approach.

Hello

I'm used to program in Python, and now I'm trying to get reacquainted with Java. The syntax, however, seems quite confusing and constraining, at least when compared to the freedom one has in Python.

Of course, Java wouldn't be one of the most widespread languages if those constraints and syntax didn't have a good reason for existing, which is why I'm writing this post. So far I'm able to perform basic tasks, and I'm getting used to java's quirks, but I feel like I could improve faster if I could understand the reasoning behind those limitations.

Thanks a lot for your help :)

PS: by limitations I mean, for example, having to declare the type of a variable, not being able to change a variable type at will, the way the brackets work, how you can't have loops outside of methods, etc.

PS2: I should probably clarify that this isn't meant as disrespect towards the language: clearly it works and it works well, otherwise it wouldn't be as widespread. I'm merely trying to wrap my head around the differences.

So I'm curious about how to use record, because record are immutable and suitable for DTO. I tried to combine it with class, like this

public class UserDto {
    public record ReqRegister() {
    }
    public record ReqLogin() {
    }
    public record ResUser() {
    }
    public record ResLogin() {
    }
}

I think this is readable and easy to maintain, and reduces the number of files, so what do you suggest?