com.aspectran.core.util.ArrayStack Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2023 The Aspectran Project
*
* Licensed 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 com.aspectran.core.util;
import java.util.ArrayList;
import java.util.EmptyStackException;
/**
* This class is a clone of org.apache.commons.collections4.ArrayStack
*
* 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 #pop()} method removes
* them from the top down.
*
* Unlike Stack, ArrayStack accepts null entries.
*
* @param the type of elements in this list
* @see java.util.Stack
*/
public class ArrayStack extends ArrayList {
/** Ensure serialization compatibility. */
private static final long serialVersionUID = 4952513157310856314L;
/**
* 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);
}
/**
* 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 E peek() throws EmptyStackException {
int n = size();
if (n <= 0) {
throw new EmptyStackException();
}
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 E peek(int n) throws EmptyStackException {
int m = (size() - n) - 1;
if (m < 0) {
throw new EmptyStackException();
}
return get(m);
}
public E peek(Class target) throws EmptyStackException {
for (int i = size() - 1; i >= 0; i--) {
E item = get(i);
if (item.getClass().equals(target)) {
return item;
}
}
throw new EmptyStackException();
}
/**
* 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 E pop() throws EmptyStackException {
int n = size();
if (n <= 0) {
throw new EmptyStackException();
}
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 E push(E item) {
add(item);
return item;
}
/**
* Replaces the top item of this stack with another item without removing it.
*
* @return the top item previously on the stack
* @throws EmptyStackException if the stack is empty
*/
public E update(E item) throws EmptyStackException {
int n = size();
if (n <= 0) {
throw new EmptyStackException();
}
return set(n - 1, item);
}
/**
* Replaces the n'th item down (zero-relative) from the top of this
* stack with another item without removing it.
*
* @param n the number of items down to go
* @return the n'th item previously on the stack, zero relative
* @throws EmptyStackException if there are not enough items on the
* stack to satisfy this request
*/
public E update(int n, E item) throws EmptyStackException {
int m = (size() - n) - 1;
if (m < 0) {
throw new EmptyStackException();
}
return set(m, 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(E object) {
int i = size() - 1; // Current index
int n = 1; // Current distance
while (i >= 0) {
Object current = get(i);
if ((object == null && current == null) ||
(object != null && object.equals(current))) {
return n;
}
i--;
n++;
}
return -1;
}
}