Builder pattern for polymorphic object hierarchy: possible with Java?

Question

I have a hierarchy of interfaces, with Child implementing Parent. I would like to work with immutable objects, so I would like to design Bui

Answer 1

maybe like this without builders?:

interface P {
    public Long getParentProperty();
}
interface C1 extends P {
    public Integer getChild1Property();
}
interface C2 extends P {
    public String getChild2PropertyA();
    public Object getChild2PropertyB();
}
abstract class PABC implements P {
    @Override public final Long getParentProperty() {
        return parentLong;
    }
    protected Long parentLong;
    protected PABC setParentProperty(Long value) {
        parentLong = value;
        return this;
    }
}
final class C1Impl extends PABC implements C1 {
    protected C1Impl setParentProperty(Long value) {
        super.setParentProperty(value);
        return this;
    }
    @Override public Integer getChild1Property() {
        return n;
    }
    public C1Impl setChild1Property(Integer value) {
        n = value;
        return this;
    }
    private Integer n;
}
final class C2Impl extends PABC implements C2 {
    private String string;
    private Object object;

    protected C2Impl setParentProperty(Long value) {
        super.setParentProperty(value);
        return this;
    }
    @Override public String getChild2PropertyA() {
    return string;
    }

    @Override public Object getChild2PropertyB() {
        return object;
    }
    C2Impl setChild2PropertyA(String string) {
        this.string=string;
        return this;
    }
    C2Impl setChild2PropertyB(Object o) {
        this.object=o;
        return this;
    }
}
public class Myso9138027 {
    public static void main(String[] args) {
        C1Impl c1 = new C1Impl().setChild1Property(5).setParentProperty(10L);
        C2Impl c2 = new C2Impl().setChild2PropertyA("Hello").setParentProperty(10L).setChild2PropertyB(new Object());
    }
}