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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.commons.collections;
import java.util.ArrayList;
import java.util.EmptyStackException;
/**
* An implementation of the {@link java.util.Stack} API that is based on an
* ArrayList instead of a Vector, so it is not
* synchronized to protect against multi-threaded access. The implementation
* is therefore operates faster in environments where you do not need to
* worry about multiple thread contention.
*
* The removal order of an ArrayStack is based on insertion
* order: The most recently added element is removed first. The iteration
* order is not the same as the removal order. The iterator returns
* elements from the bottom up, whereas the {@link #remove()} method removes
* them from the top down.
*
* Unlike Stack, ArrayStack accepts null entries.
*
* @see java.util.Stack
* @since Commons Collections 1.0
* @version $Revision$ $Date$
*
* @author Craig R. McClanahan
* @author Paul Jack
* @author Stephen Colebourne
*
* @deprecated Apache Commons Collections version 3.x is being deprecated from AEMaaCS. The upgraded version 4.4 of Commons Collections is already included as replacement. Customers are advised to upgrade to this version of the library. Please note: the package name was changed to org.apache.commons.collections4. Further note that there are AEM APIs currently exposing the old collections classes; these will be updated in upcoming releases.
*/
@Deprecated(since = "2021-04-30")
public class ArrayStack extends ArrayList implements Buffer {
/**
* Ensure serialization compatibility
*/
private static final long serialVersionUID = 2130079159931574599L;
/**
* Constructs a new empty ArrayStack. The initial size
* is controlled by ArrayList and is currently 10.
*/
public ArrayStack() {
super();
}
/**
* Constructs a new empty ArrayStack with an initial size.
*
* @param initialSize the initial size to use
* @throws IllegalArgumentException if the specified initial size
* is negative
*/
public ArrayStack(int initialSize) {
super(initialSize);
}
/**
* Return true if this stack is currently empty.
*
* This method exists for compatibility with java.util.Stack.
* New users of this class should use isEmpty instead.
*
* @return true if the stack is currently empty
*/
public boolean empty() {
return isEmpty();
}
/**
* Returns the top item off of this stack without removing it.
*
* @return the top item on the stack
* @throws EmptyStackException if the stack is empty
*/
public Object peek() throws EmptyStackException {
int n = size();
if (n <= 0) {
throw new EmptyStackException();
} else {
return get(n - 1);
}
}
/**
* Returns the n'th item down (zero-relative) from the top of this
* stack without removing it.
*
* @param n the number of items down to go
* @return the n'th item on the stack, zero relative
* @throws EmptyStackException if there are not enough items on the
* stack to satisfy this request
*/
public Object peek(int n) throws EmptyStackException {
int m = (size() - n) - 1;
if (m < 0) {
throw new EmptyStackException();
} else {
return get(m);
}
}
/**
* Pops the top item off of this stack and return it.
*
* @return the top item on the stack
* @throws EmptyStackException if the stack is empty
*/
public Object pop() throws EmptyStackException {
int n = size();
if (n <= 0) {
throw new EmptyStackException();
} else {
return remove(n - 1);
}
}
/**
* Pushes a new item onto the top of this stack. The pushed item is also
* returned. This is equivalent to calling add.
*
* @param item the item to be added
* @return the item just pushed
*/
public Object push(Object item) {
add(item);
return item;
}
/**
* Returns the one-based position of the distance from the top that the
* specified object exists on this stack, where the top-most element is
* considered to be at distance 1. If the object is not
* present on the stack, return -1 instead. The
* equals() method is used to compare to the items
* in this stack.
*
* @param object the object to be searched for
* @return the 1-based depth into the stack of the object, or -1 if not found
*/
public int search(Object object) {
// Current index
int i = size() - 1;
// Current distance
int n = 1;
while (i >= 0) {
Object current = get(i);
if ((object == null && current == null) || (object != null && object.equals(current))) {
return n;
}
i--;
n++;
}
return -1;
}
/**
* Returns the element on the top of the stack.
*
* @return the element on the top of the stack
* @throws BufferUnderflowException if the stack is empty
*/
public Object get() {
int size = size();
if (size == 0) {
throw new BufferUnderflowException();
}
return get(size - 1);
}
/**
* Removes the element on the top of the stack.
*
* @return the removed element
* @throws BufferUnderflowException if the stack is empty
*/
public Object remove() {
int size = size();
if (size == 0) {
throw new BufferUnderflowException();
}
return remove(size - 1);
}
}