* Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.

import java.util.Iterator;

    private class ZPagesIterator implements Iterator<ZPage> {

        private ZAddressRangeMapForPageTable.Iterator mapIter;

        private ZPage next;

        ZPagesIterator() {

            mapIter = map().new Iterator();

            positionToNext();

        }

        private ZPage positionToNext() {

            ZPage current = next;

            // Find next

            ZPage found = null;

            while (mapIter.hasNext()) {

                ZPageTableEntry entry = new ZPageTableEntry(mapIter.next());

                if (!entry.isEmpty()) {

                    ZPage page = entry.page();

                    // Medium pages have repeated entries for all covered slots,

                    // therefore we need to compare against the current page.

                    if (page != null && !page.equals(current)) {

                        found = page;

                        break;

                    }

                }

            }

            next = found;

            return current;

        }

        @Override

        public boolean hasNext() {

            return next != null;

        }

        @Override

        public ZPage next() {

            return positionToNext();

        }

        @Override

        public void remove() {

            /* not supported */

        }

    }

    abstract class ZPageFilter {

        public abstract boolean accept(ZPage page);

    }

    class ZPagesFilteredIterator implements Iterator<ZPage> {

        private ZPage next;

        private ZPagesIterator iter = new ZPagesIterator();

        private ZPageFilter filter;

        ZPagesFilteredIterator(ZPageFilter filter) {

            this.filter = filter;

            positionToNext();

        }

        public ZPage positionToNext() {

            ZPage current = next;

            // Find next

            ZPage found = null;

            while (iter.hasNext()) {

                ZPage page = iter.next();

                if (filter.accept(page)) {

                    found = page;

                    break;

                }

            }

            next = found;

            return current;

        }

        @Override

        public boolean hasNext() {

            return next != null;

        }

        @Override

        public ZPage next() {

            return positionToNext();

        }

        @Override

        public void remove() {

            /* not supported */

        }

    }

    public Iterator<ZPage> iterator() {

        return new ZPagesIterator();

    }

    public Iterator<ZPage> activePagesIterator() {

        return new ZPagesFilteredIterator(new ZPageFilter() {

            public boolean accept(ZPage page) {

                return page.is_active();

            }

        });

    }