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java-help

❓︱qotw-answers

Pétrichor

7/5/2025

Android Studio "temporal must not be null"

I'm very new to Java and coding in general (I started last week) and I'm making a calendar app for android. I got the basic calendar running, but when I tried to add a feature it keeps crashing. I believed it's because of line 119 always being null, but I initialised and declared it (I think). Anyways I'm stuck on this and can't work on my app anymore, so I would be very happy to solve this! Here's the error logcat message :

FATAL EXCEPTION: main Process: com.petris.lunor, PID: 2117 java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.petris.lunor/com.petris.lunor.MainActivity}: java.lang.NullPointerException: temporal must not be null at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4186) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4467) with tag AndroidRuntime

FATAL EXCEPTION: main Process: com.petris.lunor, PID: 2117 java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.petris.lunor/com.petris.lunor.MainActivity}: java.lang.NullPointerException: temporal must not be null at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4186) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4467) with tag AndroidRuntime

...

Westu

7/4/2025

Single JVM process architecture

Hi everyone, I’m working on a Java project that will run entirely in a single JVM (deployed via Docker Compose). Inside the JVM I will have “services” which will handle the business logic. Each service/replica will run in a separate thread giving me async processing. The architecture which I’m going with will pull data from APIs into rabbitmq queue on a set schedule during the day. ...

Kishore

7/4/2025

RequestRejectExpection

Getting this error in spring boot

Murat

7/4/2025

Help, target folder saves to src, what should I do?

Hello everyone, I started saving the plugin and for some reason the target folder appears in src. This happened today, I couldn’t fix it, I went to write an anti-cheat and now this is happening again. Can you please help?

Abdullah

7/3/2025

Scene Builder

i like to write direct in Fxml file rather then using scene builder. My question is will i lose good tool if i did not use it and is it irreplaceable?...

1howard1.

7/3/2025

Does anyone have resource(e-book or web) for beginer learning API

with Java (framework=spring)

Nighty

7/3/2025

Can someone help me what is this type of issue, i am new to Java

i don't know my code is not wrong but still no working , i have asked my friend and he said "why u use maven to run , can someone help me please

𐌋okesh

7/3/2025

Suffering to understand Threading

[cross-posted, please don't ban me, I apologize if that's prohibited] Heyy guys! I hope y'all doing great. lets clear some concepts today (to me). This is from Oracle javase jls specs:

While most of the discussion in the preceding chapters is concerned only with the behavior of code as executed a single statement or expression at a time, that is, by a single thread, the Java Virtual Machine can support many threads of execution at once.

While most of the discussion in the preceding chapters is concerned only with the behavior of code as executed a single statement or expression at a time, that is, by a single thread, the Java Virtual Machine can support many threads of execution at once.

...

coolsigma103

7/3/2025

finding a opengl-based gui library for lwjgl

im making a game engine and need gui library for the editor thats clean and optomized(idk if i spelled right)

Fixzy

7/3/2025

A java exception has been occured

Im making my own minecraft server project but im gettin the same error; I made a client and a server cmllib doesnt launches my client so i wanna launch it with java args on my c# launcher the startup code: // Java exe yolu (Java 8 JRE veya JDK yüklü olmalı)...

Kennedy Antonio

7/2/2025

I'd love to learn about Java

I would like to learn about Java deeply.

Thorinwasher

7/2/2025

Merging completable future results - Good practices

Is this a bad idea? ```java public static <T> CompletableFuture<List<T>> mergeFutures(List<CompletableFuture<T>> completableFutureList) { if (completableFutureList.isEmpty()) { return CompletableFuture.completedFuture(List.of());...

coolsigma103

7/2/2025

how to run java belong with cpp

im making a game engine in cpp but the scripting and editor will be written in java, whats the best way to link those 2 thing

Steadhaven

7/1/2025

Java network programming

Why are there literally no java books that go in depth about network programming? I am talking about the JDK 11 HttpClient, or working with certificates/sso tokens through TrustManager or KeyManagerFactory/SSLContext and like. I have searched and searched, and the only thing that comes near is an ancient outdated 4th edition "Java Networks Programming" which is made before jdk11 and thus have no HttpCllent. And before you say docs.. theyre not explaining anything or go deep. You have to know what to look for and why you would use it. I need something that covers a broad area going deep and showing practical ways of using it. Please let me know if you have any relatively up to date resources. Anything newer than jdk11 is acceptable....

Prateek Chaudhary 🫅🏻

7/1/2025

How can you assist me in java development

Java development assistance needed.

L4yoos

7/1/2025

System of Cookies with your Auth System should be in Controller or maybe Service?

Where i should put logic of Cookie System? Thanks in advance

1howard1.

7/1/2025

Spring boot upload files with multiple parameter

How do i upload file with multiple parameter in spring boot in submit form Thanks in advance...

L4yoos

6/30/2025

Why and when we should use package-private in hexagonal architecture?

Hello everyone, I come with a question because I am learning hexagonal architecture when, how and why do we use package-private in this architecture I would like someone to explain it to me in plain English or maybe someone knows a good tutorial on YouTube? Thanks in advance!

𝓖𝓾𝓻𝔀𝓲𝟑𝟎

6/30/2025

Use BBModel's in spigot plugin

Im tring to create a vehicles plugin that supports bbmodel' s, for the actual model, animations and hitboxes, but i can't find much online on how to do it. I've written all the models to convert the actual .bbmodel json to java objects, but now i don't know how to actually proceed with the entity generation and that kind of stuff.

Hellobrowooo

6/30/2025

Help

What is 5+5-2

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Java Community | Help. Code. Learn.

We are a Community full of Java developers. Connect with other devs, get help, help others and do much more!

Java Community | Help. Code. Learn.

We are a Community full of Java developers. Connect with other devs, get help, help others and do much more!