Examples of org.apache.commons.collections.iterators.IteratorChain

Package org.apache.commons.collections.iterators

Examples of org.apache.commons.collections.iterators.IteratorChain

org.apache.commons.collections.iterators.IteratorChain
An IteratorChain is an Iterator that wraps a number of Iterators.
This class makes multiple iterators look like one to the caller When any method from the Iterator interface is called, the IteratorChain will delegate to a single underlying Iterator. The IteratorChain will invoke the Iterators in sequence until all Iterators are exhausted.
Under many circumstances, linking Iterators together in this manner is more efficient (and convenient) than reading out the contents of each Iterator into a List and creating a new Iterator.
Calling a method that adds new Iteratorafter a method in the Iterator interface has been called will result in an UnsupportedOperationException. Subclasses should take care to not alter the underlying List of Iterators.
NOTE: As from version 3.0, the IteratorChain may contain no iterators. In this case the class will function as an empty iterator. @since Commons Collections 2.1 @version $Revision: 647116 $ $Date: 2008-04-11 12:23:08 +0100 (Fri, 11 Apr 2008) $ @author Morgan Delagrange @author Stephen Colebourne

    final AtomicBoolean scanning = new AtomicBoolean(false);
    Instance instance = opts.getInstance();
    MetaDataTableScanner rootScanner = new MetaDataTableScanner(instance, SecurityConstants.getSystemCredentials(), Constants.METADATA_ROOT_TABLET_KEYSPACE);
    MetaDataTableScanner metaScanner = new MetaDataTableScanner(instance, SecurityConstants.getSystemCredentials(), Constants.NON_ROOT_METADATA_KEYSPACE);
    @SuppressWarnings("unchecked")
    Iterator<TabletLocationState> scanner = (Iterator<TabletLocationState>)new IteratorChain(rootScanner, metaScanner);
    LiveTServerSet tservers = new LiveTServerSet(instance, DefaultConfiguration.getDefaultConfiguration(), new Listener() {
      @Override
      public void update(LiveTServerSet current, Set<TServerInstance> deleted, Set<TServerInstance> added) {
        if (!deleted.isEmpty() && scanning.get())
          log.warn("Tablet servers deleted while scanning: " + deleted);

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  public Iterator<Entry<Key,Value>> iterator() {
    if (ranges == null) {
      throw new IllegalStateException("ranges not set");
    }


    IteratorChain chain = new IteratorChain();
    for (Range range : ranges) {
      SortedKeyValueIterator<Key,Value> i = new SortedMapIterator(table.table);
      try {
        i = createFilter(i);
        i.seek(range, createColumnBSS(fetchedColumns), !fetchedColumns.isEmpty());
        chain.addIterator(new IteratorAdapter(i));
      } catch (IOException e) {
        throw new RuntimeException(e);
      }
    }
    return chain;

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     * @param iterator2
     * @return
     */
    @SuppressWarnings("unchecked")
    public static <T> Iterator<T> chain(Iterator<? extends T> iterator1, Iterator<? extends T> iterator2) {
        return new IteratorChain(iterator1, iterator2);
    }

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     * @param iterators
     * @return
     */
    @SuppressWarnings("unchecked")
    public static <T> Iterator<T> chain(Iterator<? extends T>[] iterators) {
        return new IteratorChain(iterators);
    }

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     * @param iterators
     * @return
     */
    @SuppressWarnings("unchecked")
    public static <T> Iterator<T> chain(Collection<? extends T> iterators) {
        return new IteratorChain(iterators);
    }

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        } catch (RepositoryException re) {
            log.warn("inconsistent hierarchy state", re);
        }
        // create an iterator over the collected descendants
        // in decreasing depth order
        IteratorChain resultIter = new IteratorChain();
        for (int i = la.length - 1; i >= 0; i--) {
            List list = la[i];
            if (list != null) {
                resultIter.addIterator(list.iterator());
            }
        }
        /**
         * if the resulting iterator chain is empty return
         * EMPTY_LIST.iterator() instead because older versions
         * of IteratorChain (pre Commons Collections 3.1)
         * would throw UnsupportedOperationException in this
         * situation
         */
        if (resultIter.getIterators().isEmpty()) {
            return Collections.EMPTY_LIST.iterator();
        }
        return resultIter;
    }

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        } catch (RepositoryException re) {
            log.warn("inconsistent hierarchy state", re);
        }
        // create an iterator over the collected descendants
        // in decreasing depth order
        IteratorChain resultIter = new IteratorChain();
        for (int i = la.length - 1; i >= 0; i--) {
            List list = la[i];
            if (list != null) {
                resultIter.addIterator(list.iterator());
            }
        }
        /**
         * if the resulting iterator chain is empty return
         * EMPTY_LIST.iterator() instead because older versions
         * of IteratorChain (pre Commons Collections 3.1)
         * would throw UnsupportedOperationException in this
         * situation
         */
        if (resultIter.getIterators().isEmpty()) {
            return Collections.EMPTY_LIST.iterator();
        }
        return resultIter;
    }

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     * @param iterator2  the first iterators to use, not null
     * @return a combination iterator over the iterators
     * @throws NullPointerException if either iterator is null
     */
    public static Iterator chainedIterator(Iterator iterator1, Iterator iterator2) {
        return new IteratorChain(iterator1, iterator2);
    }

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     * @param iterators  the iterators to use, not null or empty or contain nulls
     * @return a combination iterator over the iterators
     * @throws NullPointerException if iterators array is null or contains a null
     */
    public static Iterator chainedIterator(Iterator[] iterators) {
        return new IteratorChain(iterators);
    }

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     * @return a combination iterator over the iterators
     * @throws NullPointerException if iterators collection is null or contains a null
     * @throws ClassCastException if the iterators collection contains the wrong object type
     */
    public static Iterator chainedIterator(Collection iterators) {
        return new IteratorChain(iterators);
    }

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