package it.unimi.dsi.fastutil;
/*
* fastutil: Fast & compact type-specific collections for Java
*
* Copyright (C) 2002-2008 Sebastiano Vigna
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
import java.util.NoSuchElementException;
/** A stack.
*
* <P>A stack must provide the classical {@link #push(Object)} and
* {@link #pop()} operations, but may be also <em>peekable</em>
* to some extent: it may provide just the {@link #top()} function,
* or even a more powerful {@link #peek(int)} method that provides
* access to all elements on the stack (indexed from the top, which
* has index 0).
*/
public interface Stack<K> {
/** Pushes the given object on the stack.
*
* @param o the object that will become the new top of the stack.
*/
void push( K o );
/** Pops the top off the stack.
*
* @return the top of the stack.
* @throws NoSuchElementException if the stack is empty.
*/
K pop();
/** Checks whether the stack is empty.
*
* @return true if the stack is empty.
*/
boolean isEmpty();
/** Peeks at the top of the stack (optional operation).
*
* @return the top of the stack.
* @throws NoSuchElementException if the stack is empty.
*/
K top();
/** Peeks at an element on the stack (optional operation).
*
* @return the <code>i</code>-th element on the stack; 0 represents the top.
* @throws IndexOutOfBoundsException if the designated element does not exist..
*/
K peek( int i );
}
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