SortedArrayList.java

// Copyright (c) 2003-present, Jodd Team (http://jodd.org)
// All rights reserved.
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package org.springside.modules.utils.collection.type;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.Iterator;

/**
 * 从Jodd整体复制，部分指定了index的操作不支持，如 add(index, element)
 * 
 * An extension of <code>ArrayList</code> that insures that all of the items
 * added are sorted. <b>This breaks original list contract!</b>.
 * A binary search method is used to provide a quick way to
 * auto sort this list.Note: Not all methods for adding and
 * removing elements are supported.
 */
public class SortedArrayList<E> extends ArrayList<E> {

	private static final long serialVersionUID = -8301136559614447593L;

	protected final Comparator<? super E> comparator;

	/**
	 * Constructs a new <code>SortedArrayList</code>.
	 */
	public SortedArrayList(Comparator<? super E> c) {
		comparator = c;
	}

	/**
	 * Constructs a new <code>SortedArrayList</code> expecting
	 * elements are comparable.
	 */
	public SortedArrayList() {
		comparator = null;
	}

	/**
	 * Constructs a new <code>SortedArrayList</code> expecting
	 * elements are comparable.
	 */
	public SortedArrayList(Collection<? extends E> c) {
		comparator = null;
		addAll(c);
	}

	/**
	 * Returns comparator assigned to this collection, if such exist.
	 */
	public Comparator getComparator() {
		return comparator;
	}

	// ---------------------------------------------------------------- override

	/**
	 * Adds an Object to sorted list. Object is inserted at correct place, found
	 * using binary search. If the same item exist, it will be put to the end of
	 * the range.
	 * <p>
	 * This method breaks original list contract since objects are not
	 * added at the list end, but in sorted manner.
	 */
	@Override
	public boolean add(E o) {
		int idx = 0;
		if (!isEmpty()) {
			idx = findInsertionPoint(o);
		}
		super.add(idx, o);
		return true;
	}

	/**
	 * Add all of the elements in the given collection to this list.
	 */
	@Override
	public boolean addAll(Collection<? extends E> c) {
		Iterator<? extends E> i = c.iterator();
		boolean changed = false;
		while (i.hasNext()) {
			boolean ret = add(i.next());
			if (!changed) {
				changed = ret;
			}
		}
		return changed;
	}

	/**
	 * Finds the index at which object should be inserted.
	 */
	public int findInsertionPoint(E o) {
		return findInsertionPoint(o, 0, size() - 1);
	}

	// ---------------------------------------------------------------- unsupported methods

	/**
	 * @throws UnsupportedOperationException This method not supported.
	 */
	@Override
	@Deprecated
	public void add(int index, E element) {
		throw new UnsupportedOperationException();
	}

	/**
	 * @throws UnsupportedOperationException This method not supported.
	 */
	@Override
	@Deprecated
	public E set(int index, E element) {
		throw new UnsupportedOperationException();
	}

	/**
	 * @throws UnsupportedOperationException This method not supported.
	 */
	@Override
	@Deprecated
	public boolean addAll(int index, Collection<? extends E> c) {
		throw new UnsupportedOperationException();
	}


	// ---------------------------------------------------------------- sorting

	/**
	 * Compares two keys using the correct comparison method for this
	 * collection.
	 */
	@SuppressWarnings( {"unchecked"})
	protected int compare(E k1, E k2) {
		if (comparator == null) {
			return ((Comparable) k1).compareTo(k2);
		}
		return comparator.compare(k1, k2);
	}

	/**
	 * Conducts a binary search to find the index where Object
	 * should be inserted.
	 */
	protected int findInsertionPoint(E o, int low, int high) {

		while (low <= high) {
			int mid = (low + high) >>> 1;
			int delta = compare(get(mid), o);

			if (delta > 0) {
				high = mid - 1;
			} else {
				low = mid + 1;
			}
		}

		return low;
	}

}