package java.util;
public class ArrayList<E> extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{
// 版本号
private static final long serialVersionUID = L;
private transient Object[] elementData;
private int size;
// ArrayList带容量大小的构造函数。
public ArrayList(int initialCapacity) {
super();
if (initialCapacity < )
throw new IllegalArgumentException("Illegal Capacity: "+
initialCapacity);
this.elementData = new Object[initialCapacity];
}
// 默认容量是10。
public ArrayList() {
this();
}
// 创建一个包含collection的ArrayList
public ArrayList(Collection<? extends E> c) {
elementData = c.toArray();
size = elementData.length;
if (elementData.getClass() != Object[].class)
elementData = Arrays.copyOf(elementData, size, Object[].class);
}
public void trimToSize() {
modCount++;
int oldCapacity = elementData.length;
if (size < oldCapacity) {
elementData = Arrays.copyOf(elementData, size);
}
}
// 确定ArrarList的容量。
// 若ArrayList的容量不足以容纳当前的全部元素,设置 新的容量=“(原始容量x3)/2 + 1”
public void ensureCapacity(int minCapacity) {
// 将“修改统计数”+1,该变量主要是用来实现fail-fast机制的
modCount++;
int oldCapacity = elementData.length;
if (minCapacity > oldCapacity) {
Object oldData[] = elementData;
int newCapacity = (oldCapacity * )/ + ;
//如果还不够,则直接将minCapacity设置为当前容量
if (newCapacity < minCapacity)
newCapacity = minCapacity;
elementData = Arrays.copyOf(elementData, newCapacity);
}
}
public boolean add(E e) {
ensureCapacity(size + );
elementData[size++] = e;
return true;
}
public int size() {
return size;
}
public boolean contains(Object o) {
return indexOf(o) >= ;
}
public boolean isEmpty() {
return size == ;
}
public int indexOf(Object o) {
if (o == null) {
for (int i = ; i < size; i++)
if (elementData[i]==null)
return i;
} else {
for (int i = ; i < size; i++)
if (o.equals(elementData[i]))
return i;
}
return -;
}
public int lastIndexOf(Object o) {
if (o == null) {
for (int i = size-; i >= ; i--)
if (elementData[i]==null)
return i;
} else {
for (int i = size-; i >= ; i--)
if (o.equals(elementData[i]))
return i;
}
return -;
}
public int lastIndexOf(Object o) {
if (o == null) {
for (int i = size-; i >= ; i--)
if (elementData[i]==null)
return i;
} else {
for (int i = size-; i >= ; i--)
if (o.equals(elementData[i]))
return i;
}
return -;
}
public Object[] toArray() {
return Arrays.copyOf(elementData, size);
}
// 返回数组
public <T> T[] toArray(T[] a) {
if (a.length < size)
return (T[]) Arrays.copyOf(elementData, size, a.getClass());
System.arraycopy(elementData, , a, , size);
if (a.length > size)
a[size] = null;
return a;
}
// 获取index的元素值
public E get(int index) {
RangeCheck(index);
return (E) elementData[index];
}
public E set(int index, E element) {
RangeCheck(index);
E oldValue = (E) elementData[index];
elementData[index] = element;
return oldValue;
}
// 添加
public boolean add(E e) {
ensureCapacity(size + ); // Increments modCount!!
elementData[size++] = e;
return true;
}
// 添加到指定位置
public void add(int index, E element) {
if (index > size || index < )
throw new IndexOutOfBoundsException(
"Index: "+index+", Size: "+size);
ensureCapacity(size+); // Increments modCount!!
System.arraycopy(elementData, index, elementData, index + ,
size - index);
elementData[index] = element;
size++;
}
// 删除指定位置的元素
public E remove(int index) {
RangeCheck(index);
modCount++;
E oldValue = (E) elementData[index];
int numMoved = size - index - ;
if (numMoved > )
System.arraycopy(elementData, index+, elementData, index,
numMoved);
elementData[--size] = null;
return oldValue;
}
// 删除指定元素
public boolean remove(Object o) {
if (o == null) {
for (int index = ; index < size; index++)
if (elementData[index] == null) {
fastRemove(index);
return true;
}
} else {
for (int index = ; index < size; index++)
if (o.equals(elementData[index])) {
fastRemove(index);
return true;
}
}
return false;
}
private void fastRemove(int index) {
modCount++;
int numMoved = size - index - ;
// 从"index+1"开始,用后面的元素替换前面的元素。
if (numMoved > )
System.arraycopy(elementData, index+, elementData, index,
numMoved);
// 将最后一个元素设为null
elementData[--size] = null; // Let gc do its work
}
// 删除元素
public boolean remove(Object o) {
if (o == null) {
for (int index = ; index < size; index++)
if (elementData[index] == null) {
fastRemove(index);
return true;
}
} else {
// 便利ArrayList,找到“元素o”,则删除,并返回true。
for (int index = ; index < size; index++)
if (o.equals(elementData[index])) {
fastRemove(index);
return true;
}
}
return false;
}
// 清空ArrayList,将全部的元素设为null
public void clear() {
modCount++;
for (int i = ; i < size; i++)
elementData[i] = null;
size = ;
}
// 将集合c追加到ArrayList中
public boolean addAll(Collection<? extends E> c) {
Object[] a = c.toArray();
int numNew = a.length;
ensureCapacity(size + numNew);
System.arraycopy(a, , elementData, size, numNew);
size += numNew;
return numNew != ;
}
public boolean addAll(int index, Collection<? extends E> c) {
if (index > size || index < )
throw new IndexOutOfBoundsException(
"Index: " + index + ", Size: " + size);
Object[] a = c.toArray();
int numNew = a.length;
ensureCapacity(size + numNew);
int numMoved = size - index;
if (numMoved > )
System.arraycopy(elementData, index, elementData, index + numNew,
numMoved);
System.arraycopy(a, , elementData, index, numNew);
size += numNew;
return numNew != ;
}
// 删除fromIndex到toIndex之间的全部元素。
protected void removeRange(int fromIndex, int toIndex) {
modCount++;
int numMoved = size - toIndex;
System.arraycopy(elementData, toIndex, elementData, fromIndex,
numMoved);
// Let gc do its work
int newSize = size - (toIndex-fromIndex);
while (size != newSize)
elementData[--size] = null;
}
private void RangeCheck(int index) {
if (index >= size)
throw new IndexOutOfBoundsException(
"Index: "+index+", Size: "+size);
}
// 克隆方法
public Object clone() {
try {
ArrayList<E> v = (ArrayList<E>) super.clone();
v.elementData = Arrays.copyOf(elementData, size);
v.modCount = ;
return v;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError();
}
}
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException{
int expectedModCount = modCount;
s.defaultWriteObject();
s.writeInt(elementData.length);
for (int i=; i<size; i++)
s.writeObject(elementData[i]);
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
}
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
// Read in size, and any hidden stuff
s.defaultReadObject();
int arrayLength = s.readInt();
Object[] a = elementData = new Object[arrayLength];
for (int i=; i<size; i++)
a[i] = s.readObject();
}
}