👀 Views: 23 💬 Answers: 1 📅 Created: 2025-07-22

java serialization hashmap Java

I'm stuck trying to I've spent hours debugging this and I'm working on a personal project and I'm working on a project and hit a roadblock. I'm experiencing an scenario with serializing a `HashMap` that contains custom objects in Java 17. When I try to serialize the map, I receive a `java.io.NotSerializableException` for my custom object, even though I've implemented `Serializable` on the class. My custom object looks like this: ```java import java.io.Serializable; public class MyCustomObject implements Serializable { private static final long serialVersionUID = 1L; private String name; private int id; public MyCustomObject(String name, int id) { this.name = name; this.id = id; } // getters and setters } ``` I've initialized my `HashMap` like this: ```java import java.util.HashMap; import java.util.Map; public class Main { public static void main(String[] args) { Map<String, MyCustomObject> customMap = new HashMap<>(); customMap.put("obj1", new MyCustomObject("First Object", 1)); // Serialization logic } } ``` When I attempt to serialize the `customMap`, I use `ObjectOutputStream`, but the process fails with the following behavior: ``` Exception in thread "main" java.io.NotSerializableException: MyCustomObject ``` I've double-checked that all member variables of `MyCustomObject` are also serializable types (String and int). I even tried adding a no-arg constructor, thinking that might be an scenario. However, I still encounter the same question. Is there something I'm missing in the serialization process, or do I need to handle the `HashMap` in a specific way? Any advice would be greatly appreciated. I'm working on a API that needs to handle this. I'd really appreciate any guidance on this. What's the best practice here? I'm working in a Linux environment. Any ideas what could be causing this? I'm using Java stable in this project.