在抽象类上实现ID的一种优雅方法

Question

I have an abstract class. I want that every instance has a unique ID. I have implemented:

public abstract class MyAbstractClass{

    static AtomicInteger nextId = new AtomicInteger();
    private int id;

    public MyAbstractClass() {
        id = nextId.incrementAndGet();
    }
}

public class MyClass extends MyAbstractClass {

       public MyClass(){
             super();
       }
}

This approach works except the part there is nothing forcing the subclass to call the constructor.

Is there a way to implement a global ID for an abstract class?

Answer 1

there is nothing forcing the subclass to call the constructor.

There is nothing you can do to stop the subclass from calling super() unless parent constructors are built hierarchically wrong.

By "hierarchically wrong", I meant there is a parent constructor that isn't based on its no-argument constructor. For instance,

public MyAbstractClass() {
    id = nextId.incrementAndGet();
}

public MyAbstractClass(String s) {
    // ignores to call this();
}

Otherwise, any child will eventually call super() , and, thus, trigger your id initialisation.