Java: Interface with new keyword how is that possible?

Question

I was reading some sourcecode from Java libraries, and I am confused here;

This code is from Document.java in jaxb library, and ContentVisitor is an Interfac

Answer 1

In the code, you're not creating an instance of the interface. Rather, the code defines an anonymous class that implements the interface, and instantiates that class.

The code is roughly equivalent to:

public final class Document {

    private final class AnonymousContentVisitor implements ContentVisitor {

        public void onStartDocument() {
            throw new IllegalStateException();
        }

        public void onEndDocument() {
            out.endDocument();
        }

        public void onEndTag() {
            out.endTag();
            inscopeNamespace.popContext();
            activeNamespaces = null;
        }
    }

    private final ContentVisitor visitor = new AnonymousContentVisitor();
}