CODEWITHSUNDEEP
java
JME
JME

Reputation: 2353

Creating a parent class that contains an object restricted to a child class

I am attempting to make a parent class that has an object element within it, but I want to restrict this object to a type that extends the parent class. I have tried using generics in the form of

<T extends ParentClass> T

but this doesn't work.

Here is an example of what I am I currently working with.

public class ParentEvent {
    private Object event;
    private String type;
    private Date time;
    private String id;

    public ParentEvent() {
        event = null;
        type = null;
        time = null;
        id = null;
    }

    public ParentEvent(String type, String id, Date time, Object event) {
        this.event = event;
        this.type = type;
        this.time = time;
        this.id = id;
    }

    public Object getEvent() { return event; }

    public void setEvent(Object event) { this.event = event; }

    // Other get/set methods removed for clarity
}

How would I go about restricting the Object referenced in the above code to one that extends the parent class?

Upvotes: 0

Views: 90

Answers (2)

ntoskrnl
ntoskrnl

Reputation: 5744

This doesn't need generics. private ParentEvent event; should do exactly what you're after. You may also want to make ParentEvent abstract.

Upvotes: 0

darijan
darijan

Reputation: 9785

Do you mean this:

public class ParentEvent<T extends ParentEvent<?>>
{
    private T event;
    ...   
    public T getEvent() {...}
    ...
    public void setEvent(T event) { ... } 
}

And then, the child is:

public class ChildEvent extends ParentEvent<ChildEvent>

Upvotes: 1

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