/*
 * @(#) Indexable.java - Read-only interface for indexed containers.
 * (c) 2000 Ivan Maidanski <ivmai@chat.ru> http://ivmai.chat.ru
 * Freeware class library sources. All rights reserved.
 **
 * Language: Java [pure]
 * Tested with: JDK v1.1.6
 * Last modified: 2000-12-23 21:25:00 GMT+03:00
 */

/*
 * This software is the proprietary information of the author.
 **
 * Permission to use, copy, and distribute this software and its
 * documentation for non-commercial purposes and without fee is
 * hereby granted provided that this copyright notice appears in all
 * copies.
 **
 * This software should not be modified in any way; any found bug
 * should be reported to the author.
 **
 * The author disclaims all warranties with regard to this software,
 * including all implied warranties of merchantability and fitness.
 * In no event shall the author be liable for any special, indirect
 * or consequential damages or any damages whatsoever resulting from
 * loss of use, data or profits, whether in an action of contract,
 * negligence or other tortuous action, arising out of or in
 * connection with the use or performance of this software.
 */

package ivmai.util;

/**
 * Read-only interface for indexed containers.
 **
 * This interface should be implemented by a class that contains a
 * group of (typed) elements and allows at least read-only access to
 * these elements by an integer index (from <CODE>0</CODE> to
 * <CODE>length() - 1</CODE>, inclusive).
 **
 * @version 2.0
 * @author Ivan Maidanski
 **
 * @since 2.0
 */
public interface Indexable
{

/**
 * Returns the number of elements in <CODE>this</CODE> container.
 **
 * This method should not be <CODE>final</CODE>.
 **
 * @return
 * amount (non-negative value) of elements.
 **
 * @see #getAt(int)
 */
 public abstract int length();

/**
 * Returns value of the element at the specified index.
 **
 * If the value to return is primitive then it is being wrapped.
 * This method should not be <CODE>final</CODE>.
 **
 * @param index
 * the index (must be in the range) at which to return an element.
 * @return
 * an element (may be <CODE>null</CODE>) at <VAR>index</VAR>.
 * @exception ArrayIndexOutOfBoundsException
 * if <VAR>index</VAR> is negative or is not less than
 * <CODE>length()</CODE>.
 * @exception OutOfMemoryError
 * if there is not enough memory.
 **
 * @see #length()
 */
 public abstract Object getAt(int index)
  throws ArrayIndexOutOfBoundsException;
}