package com.qsq.study;
import java.util.Arrays;
public class ArrayList<E> implements List<E> {
private static final int DEFAULT_CAPACITY = 16;
private static final Object[] EMPTY_ELEMENT_DATA = {};
private Object[] elementData;
private int size = 0;
/*
* ����һ��Ĭ��������ArrayList
*/
public ArrayList() {
this(DEFAULT_CAPACITY);
}
/*
* ����һ��ָ����ʼ������ArrayList
*
* @param initialCapacity ��ʼ����
*
* @throws IllegalArgumentException ָ����ʼ����Ϊ����ʱ�׳��Ƿ������쳣
*/
public ArrayList(int initialCapacity) {
if (initialCapacity > 0) {
this.elementData = new Object[initialCapacity];
} else if (initialCapacity == 0) {
this.elementData = EMPTY_ELEMENT_DATA;
} else {
throw new IllegalArgumentException("Illegal Capacity " + initialCapacity);
}
}
@Override
public int size() {
return this.size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
/*
* ����elementData��������
*
* @param capacity �µ���������
*/
private void grow(int capacity) {
if (capacity < elementData.length) {
return;
}
elementData = Arrays.copyOf(elementData, capacity);
}
@Override
public boolean add(E e) {
if (size == elementData.length) {
grow(size * 2);
}
elementData[size++] = e;
return true;
}
@Override
public E remove(int index) {
rangeCheck(index);
// move elements after index forward by 1
for (int i = index; i < size - 1; i++) {
elementData[i] = elementData[i + 1];
}
--size;
// TODO: JDK��ʵ��: 1.Ч�� 2.GC����
// System.arraycopy(elementData, index + 1, elementData, index, size -
// index - 1);
// elementData[--size] = null;
return null;
}
@Override
public boolean remove(Object o) {
int index = indexOf(o);
if (index < 0) {
return false;
}
remove(index);
return true;
}
@SuppressWarnings({ "unchecked" })
private E elementData(int index) {
return (E) elementData[index];
}
private void rangeCheck(int index) {
// TODO: JDKԴ����δ��index<0�����������Ϊ�Σ�
if (index < 0 || index >= size) {
throw new IndexOutOfBoundsException("Index:" + index + ", Size:" + size);
}
}
@Override
public E get(int index) {
rangeCheck(index);
return elementData(index);
}
@Override
public E set(int index, E element) {
rangeCheck(index);
E oldElement = elementData(index);
elementData[index] = element;
return oldElement;
}
@Override
public int indexOf(Object o) {
if (o == null) {
for (int i = 0; i < size; i++) {
if (elementData[i] == null) {
return i;
}
}
} else {
for (int i = 0; i < size; i++) {
if (o.equals(elementData[i])) {
return i;
}
}
}
return -1;
}
}