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/*
* 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.tuscany.sca.common.java.collection;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
public class CompoundIterator<T> implements Iterator<T> {
private Iterator<T>[] iterators = null;
private int index = 0;
public CompoundIterator(Iterator<T>... iterators) {
this.iterators = iterators;
}
@SuppressWarnings("unchecked")
public CompoundIterator(Collection<T>... collections) {
this.iterators = new Iterator[collections.length];
for (int i = 0; i < collections.length; i++) {
this.iterators[i] = collections[i].iterator();
}
}
public boolean hasNext() {
// if the current enum is null that means this enum is finished
if (currentIterator() == null) {
// No next enum
return false;
}
// If the current enum has more elements, lets go
return currentIterator().hasNext();
}
private Iterator<T> findNextIterator(boolean moveCursor) {
return findNextIterator(index, moveCursor);
}
private Iterator<T> findNextIterator(int cursor, boolean moveCursor) {
// next place in the array
int next = cursor + 1;
// If the cursor is still in the array
if (next < iterators.length) {
// If there is something in that place
// AND the enum is not empty
if (iterators[next] != null && iterators[next].hasNext()) {
// OK
if (moveCursor) {
index = next;
}
return iterators[next];
}
// Try next element
return findNextIterator(next, moveCursor);
}
// No more elements available
return null;
}
public T next() {
// ask for the next element of the current enum.
if (currentIterator() != null) {
return currentIterator().next();
}
// no more elements in this Enum
// We must throw a NoSuchElementException
throw new NoSuchElementException("No more elements");
}
public void remove() {
// ask for the next element of the current enum.
if (currentIterator() != null) {
currentIterator().remove();
}
// no more elements in this Enum
// We must throw a NoSuchElementException
throw new NoSuchElementException("No more elements");
}
private Iterator<T> currentIterator() {
if (iterators != null) {
if (index < iterators.length) {
Iterator<T> e = iterators[index];
if (e == null || !e.hasNext()) {
// the current enum is null or empty
// we probably want to switch to the next one
e = findNextIterator(true);
}
return e;
}
}
return null;
}
}
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