Mutable class as a child of an immutable class

Posted by deamon on Stack Overflow See other posts from Stack Overflow or by deamon
Published on 2010-03-22T16:21:49Z Indexed on 2010/03/22 16:41 UTC
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I want to have immutable Java objects like this (strongly simplyfied):

class Immutable {

    protected String name;

    public Immutable(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

}

In some cases the object should not only be readable but mutable, so I could add mutability through inheritance:

public class Mutable extends Immutable {

    public Mutable(String name) {
        super(name);
    }

    public void setName(String name) {
        super.name = name;
    }

}

While this is technically fine, I wonder if it conforms with OOP and inheritance that mutable is also of type immutable. I want to avoid the OOP crime to throw UnsupportedOperationException for immutable object, like the Java collections API does.

What do you think? Any other ideas?

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