org.eclipse.aether.util.graph.visitor.Stack Maven / Gradle / Ivy
/*
* 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.eclipse.aether.util.graph.visitor;
import java.util.AbstractList;
import java.util.NoSuchElementException;
import java.util.RandomAccess;
/**
* A non-synchronized stack with a non-modifiable list view which starts at the top of the stack. While
* {@code LinkedList} can provide the same behavior, it creates many temp objects upon frequent pushes/pops.
*/
class Stack extends AbstractList implements RandomAccess {
@SuppressWarnings("unchecked")
// CHECKSTYLE_OFF: MagicNumber
private E[] elements = (E[]) new Object[96];
// CHECKSTYLE_ON: MagicNumber
private int size;
public void push(E element) {
if (size >= elements.length) {
@SuppressWarnings("unchecked")
E[] tmp = (E[]) new Object[size + 64];
System.arraycopy(elements, 0, tmp, 0, elements.length);
elements = tmp;
}
elements[size++] = element;
}
public E pop() {
if (size <= 0) {
throw new NoSuchElementException();
}
return elements[--size];
}
public E peek() {
if (size <= 0) {
return null;
}
return elements[size - 1];
}
@Override
public E get(int index) {
if (index < 0 || index >= size) {
throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
}
return elements[size - index - 1];
}
@Override
public int size() {
return size;
}
}