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/*******************************************************************************
* Copyright (c) 2006, 2010 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Mike Kucera (IBM Corporation) - initial API and implementation
*******************************************************************************/
package org.eclipse.cdt.core.parser.util;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
/**
* Useful utility methods for dealing with Collections.
*
* @noinstantiate This class is not intended to be instantiated by clients.
*/
public final class CollectionUtils {
private CollectionUtils() {
// this class has just static utility methods
}
/**
* Returns an iterator that iterates backwards over the given list.
* The remove() method is not implemented and will throw UnsupportedOperationException.
* The returned iterator does not support the remove() method.
*
* @throws NullPointerException if list is null
*/
public static <T> Iterator<T> reverseIterator(final List<T> list) {
return new Iterator<T>() {
ListIterator<T> iterator = list.listIterator(list.size());
public boolean hasNext() {
return iterator.hasPrevious();
}
public T next() {
return iterator.previous();
}
public void remove() {
throw new UnsupportedOperationException("remove() not supported"); //$NON-NLS-1$
}
};
}
/**
* Allows a foreach loop to iterate backwards over a list
* from the end to the start.
*
* e.g.
* for(Object o : reverseIterable(list)) { ... }
*
* @throws NullPointerException if list is null
*/
public static <T> Iterable<T> reverseIterable(final List<T> list) {
return iterable(reverseIterator(list));
}
/**
* Creates an Iterable instance that just returns
* the given Iterator from its iterator() method.
*
* This is useful for using an iterator in a foreach loop directly.
*
* e.g.
*
* for(Object o : iterable(list.listIterator())) {
* // do something
* }
*
* @throws NullPointerException if list is null
*/
public static <T> Iterable<T> iterable(final Iterator<T> iter) {
if (iter == null)
throw new NullPointerException("iter parameter is null"); //$NON-NLS-1$
return new Iterable<T>() {
public Iterator<T> iterator() {
return iter;
}
};
}
/**
* Finds the first object in the heterogeneous list that is an instance of
* the given class, removes it from the list, and returns it.
* If there is not object in the list of the given type the list is left
* unmodified and null is returned.
*
* @throws NullPointerException if list or clazz is null
* @throws UnsupportedOperationException if the list's Iterator does not support the remove() method
*/
@SuppressWarnings("unchecked")
public static <T> T findFirstAndRemove(List<?> list, Class<T> clazz) {
for (Iterator<?> iter = list.iterator(); iter.hasNext();) {
Object o = iter.next();
if (clazz.isInstance(o)) {
iter.remove();
return (T) o; // safe
}
}
return null;
}
}
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