| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.commons.configuration2; |
| |
| import java.util.Iterator; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * * A specialized iterator implementation used by {@link AbstractConfiguration} |
| * to return an iteration over all keys starting with a specified prefix. |
| * |
| * <p>This class is basically a stripped-down version of the |
| * {@code FilterIterator} class of Commons Collections</p> |
| */ |
| class PrefixedKeysIterator implements Iterator<String> |
| { |
| /** Stores the wrapped iterator. */ |
| private final Iterator<String> iterator; |
| |
| /** Stores the prefix. */ |
| private final String prefix; |
| |
| /** Stores the next element in the iteration. */ |
| private String nextElement; |
| |
| /** A flag whether the next element has been calculated. */ |
| private boolean nextElementSet; |
| |
| /** |
| * Creates a new instance of {@code PrefixedKeysIterator} and sets |
| * the wrapped iterator and the prefix for the accepted keys. |
| * |
| * @param wrappedIterator the wrapped iterator |
| * @param keyPrefix the prefix of the allowed keys |
| */ |
| public PrefixedKeysIterator(final Iterator<String> wrappedIterator, final String keyPrefix) |
| { |
| iterator = wrappedIterator; |
| prefix = keyPrefix; |
| } |
| |
| /** |
| * Returns a flag whether there are more elements in the iteration. |
| * |
| * @return a flag if there is a next element |
| */ |
| @Override |
| public boolean hasNext() |
| { |
| return nextElementSet || setNextElement(); |
| } |
| |
| /** |
| * Returns the next element in the iteration. This is the next key that |
| * matches the specified prefix. |
| * |
| * @return the next element in the iteration |
| * @throws NoSuchElementException if there is no next element |
| */ |
| @Override |
| public String next() |
| { |
| if (!nextElementSet && !setNextElement()) |
| { |
| throw new NoSuchElementException(); |
| } |
| nextElementSet = false; |
| return nextElement; |
| } |
| |
| /** |
| * Removes from the underlying collection of the base iterator the last |
| * element returned by this iterator. This method can only be called if |
| * {@code next()} was called, but not after {@code hasNext()}, |
| * because the {@code hasNext()} call changes the base iterator. |
| * |
| * @throws IllegalStateException if {@code hasNext()} has already |
| * been called. |
| */ |
| @Override |
| public void remove() |
| { |
| if (nextElementSet) |
| { |
| throw new IllegalStateException("remove() cannot be called"); |
| } |
| iterator.remove(); |
| } |
| |
| /** |
| * Determines the next element in the iteration. The return value indicates |
| * whether such an element can be found. |
| * |
| * @return a flag whether a next element exists |
| */ |
| private boolean setNextElement() |
| { |
| while (iterator.hasNext()) |
| { |
| final String key = iterator.next(); |
| if (key.startsWith(prefix + ".") || key.equals(prefix)) |
| { |
| nextElement = key; |
| nextElementSet = true; |
| return true; |
| } |
| } |
| return false; |
| } |
| } |