In my use case, I want to return a user object from the lambda function as in the code below. Before posting my question, I try many similar questions like this and this but no theme solves my problem, here is my code:
public class User {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
public class AppDatabase {
private static final int NUMBER_OF_THREADS = 4;
public static final ExecutorService databaseWriteExecutor =
Executors.newFixedThreadPool(NUMBER_OF_THREADS);
}
public class MyClass {
private User mUser;
public User findUser(){
AppDatabase.databaseWriteExecutor.execute(() -> {
mUser = work();
});
return mUser;
}
public User work(){
//simulate get user from database
User user = new User();
user.setName("Toto");
return user;
}
}
public class Main {
public static void main(String[] args) {
MyClass myClass = new MyClass();
User user;
user = myClass.findUser();
System.out.println(user.getName()); //this line: Exception in thread "main" java.lang.NullPointerException
}
}
When I run this code, I get "Exception in thread" main "java.lang.NullPointerException". My question is how do I get the User object built by the work () function, but this function should run in a background thread like in code.
