package com.learn.list;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.AbstractList;
import java.util.Arrays;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import java.util.RandomAccess;
/**
* 实现 ArrayList的集合（数组）
*
*/
public class MyArrayList<E> extends AbstractList<E> implements List<E>,Serializable {
private static final long serialVersionUID = 123322323L;
/**
*default initial capacity
*/
private static final int DEFAULT_CAPACITY=10;
/**
* shared empty array instance used for empty instance
*/
private static final Object[] EMPTY_ELEMENTDATA={};
/**
* 该数组不可序列化 用数组保存元素
*/
private transient Object[] elementData;
/**
* the size of the ArrayList(the number of elements it contains)
*
*/
private int size;
public MyArrayList(int initialCapacity){
super();//AbstractList父级构造器
if(initialCapacity<0)
throw new IllegalArgumentException("Illegal Capacity"+initialCapacity);
//初始化 指定容器的大小
this.elementData=new Object[initialCapacity];
}
/**
* constructs an empty list with an initial capacity of ten
*/
public MyArrayList(){
super();
this.elementData=EMPTY_ELEMENTDATA;
}
public MyArrayList(Collection<? extends E> c){
elementData=c.toArray();
size=elementData.length;
// c.toArray might (incorrectly) not return Object[] (see 6260652)
if(elementData.getClass()!=Object[].class)
elementData=Arrays.copyOf(elementData, size,Object[].class);
}
/**
* 缩容
*/
public void trimToSize(){
modCount++;
if(size<elementData.length){
elementData=Arrays.copyOf(elementData,size);
}
}
/**
* 扩容(集合的用起来舒服的原因 就是自动扩容 也称之为可变长度的数组)
*
*/
public void ensureCapacity(int minCapacity){
int minExpand=(elementData!=EMPTY_ELEMENTDATA)?0:DEFAULT_CAPACITY;
if(minCapacity>minExpand)
ensureExplicitCapacity(minCapacity);
}
private void ensureCapacityInteral(int minCapacity){
if(elementData==EMPTY_ELEMENTDATA)
minCapacity=Math.max(DEFAULT_CAPACITY, minCapacity);
ensureExplicitCapacity(minCapacity);
}
private void ensureExplicitCapacity(int minCapacity){
modCount++;
if(minCapacity-elementData.length>0)
grow(minCapacity);
}
/**
* 数组最大不能超过 虚拟机的限制 否则 throw OutOfMemoryError
*/
private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
/**
* 扩容 的核心方法 (边界)
* @param minCapacity
*/
private void grow(int minCapacity){
int oldCapacity=elementData.length;
int newCapacity=oldCapacity+(oldCapacity>>1);//数组扩大 原来的一半
if(newCapacity-minCapacity<0)
newCapacity=minCapacity;
if(newCapacity-MAX_ARRAY_SIZE>0)
newCapacity=hugeCapacity(minCapacity);
elementData=Arrays.copyOf(elementData, newCapacity);
}
/**
* 数组 最大的容度
* @param minCapacity
* @return
*/
private static int hugeCapacity(int minCapacity){
if(minCapacity<0) //overflow
throw new OutOfMemoryError();
return (minCapacity>MAX_ARRAY_SIZE)?Integer.MAX_VALUE:MAX_ARRAY_SIZE;
}
/**
* 返回集合大小
*/
@Override
public int size() {
return size;
}
/**
* 判断集合是否为空
*/
@Override
public boolean isEmpty() {
return size==0;
}
/**
* returns <tt>true</tt> if this list contains the specified elements
* else return <tt> false</tt>
*/
@Override
public boolean contains(Object o) {
return indexOf(o) >= 0;
}
/**
*returns the index of the first occurence of the specified element
*in this list,or -1 if this list does not contain the element
*/
@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;
}
/**
*returns the index if the last occurecce of the specified element
*in this list ,or -1 if this list doex not contain the element
*/
@Override
public int lastIndexOf(Object o) {
if(o==null){
for(int i=size-1;i>=0;i--)
if(elementData[i]==null)
return i;
}else{
for(int i=size-1;i>=0;i--){
if(o.equals(elementData[i]))
return i;
}
}
return -1;
}
/**
* 返回一个浅copy ArrayList instance
*/
public Object clone() throws CloneNotSupportedException{
try {
@SuppressWarnings("unchecked")
MyArrayList<E> v=(MyArrayList<E>)super.clone();
v.elementData=Arrays.copyOf(elementData, size);
v.modCount=0;
return v;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError();
}
}
/**
* returns an array containing all of the elements in this list
*/
@Override
public Object[] toArray() {
return Arrays.copyOf(elementData, size);
}
/**
* 依据索引获得元素值
* @param index
* @return
*/
E elementData(int index){
return (E)elementData[index];
}
/**
* 根据下标获取元素
*/
@Override
public E get(int index) {
rangeCheck(index);
return elementData(index);
}
/**
* 更改指定下标的值 并返回原来的值
*/
@Override
public E set(int index, E element) {
rangeCheck(index);
E oldValue=elementData(index);
elementData[index]=element;
return oldValue;
}
/**
* append the specified element to the end of this list
*/
@Override
public boolean add(E e) {
ensureCapacityInteral(size+1); //Increaments modcount
elementData[size++]=e; //在 原来集合的大小 添加最后一个元素 即现在集合 size-1位
return true;
}
/**
* inserts the specified elements at the specified position in this list
* 原来数组中从当前位置到后面位置 都向后移一位
*/
@Override
public void add(int index, E element) {
rangeCheckForAdd(index);
ensureCapacityInteral(size+1);
//从当前位置向后移动一位
System.arraycopy(elementData, index, elementData, index+1, size-index);
elementData[index]=element;
size++;
}
/**
* removes the element at the specified position in this list
* @param index
* @return
*/
@Override
public E remove(int index) {
rangeCheck(index);
modCount++;
E oldValue=elementData(index);
int numMoved=size-index-1;//索引从0开始，最后一位 为 size -1 (是最后一位就不需要移动)
//从当前位置的后一个位置依次向前移动一个位置
if(numMoved>0)
System.arraycopy(elementData, index+1, elementData, index, numMoved);
elementData[--size]=null;//clear to let GC do its work
return oldValue;
}
/**
* removes the first occurrence of the specified element from this list
* if is is present.
* if the list does not contain the element ,it is unchanged
* @param o
* @return
*/
@Override
public boolean remove(Object o) {
if(o==null){
for(int index=0;index<size;index++)
if(elementData[index]==null){
fastRemove(index);
return true;
}
}else{
for(int index=0;index<size;index++)
if(o.equals(elementData[index])){
fastRemove(index);
return true;
}
}
return false;
}
/**
* private remove method that skips bounds checking and does not
* return the value removed
*/
private void fastRemove(int index){
modCount++;
int numMoved=size-index-1;
if(numMoved>0)
System.arraycopy(elementData, index+1, elementData, index, numMoved);
elementData[--size]=null;//clear to let GC do its work
}
/**
* removes all of the elements from this list.
* The list will be empty after this call returns
*/
@Override
public void clear() {
modCount++;
//clear to let GC do its work
for(int i=0;i<size;i++)
elementData[i]=null;
size=0;
}
/**
* 检查范围
* @param index
*/
private void rangeCheck(int index){
if(index>=size)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
/**
* a version of rangecheck by used by add and addAll
* @param index
*/
private void rangeCheckForAdd(int index){
if(index>size||index<0)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
private String outOfBoundsMsg(int index){
return "Index:"+index+",Size:"+size;
}
@Override
public boolean containsAll(Collection<?> c) {
return false;
}
/**
* Appends all of the elements in the specified collection to the end of this
* list
*/
@Override
public boolean addAll(Collection<? extends E> c) {
Object[] a=c.toArray();
int numNew=a.length;
ensureCapacityInteral(size+numNew);//Increments modCount
System.arraycopy(a, 0, elementData, size, numNew);
size+=numNew;
return numNew!=0;
}
/**
* Inserts all of the elements in the specified collection into this list,
* starting at the specified position.
* @param index
* @param c
* @return
*/
@Override
public boolean addAll(int index, Collection<? extends E> c) {
rangeCheckForAdd(index);
Object[] a=c.toArray();
int numNew=a.length;
ensureCapacityInteral(size+numNew);
int numMoved=size-index;
if(numMoved>0)
System.arraycopy(elementData, index, elementData, index+numNew, numMoved);
System.arraycopy(a, 0, elementData, index, numNew);
size+=numNew;
return numNew!=0;
}
/**
* Removes from this list all of the elements whose index is between
* [fromIndex,toIndex) fromIndex inclusive,toIndex exclusize
* @param fromIndex
* @param toIndex
*/
protected void removeRange(int fromIndex,int toIndex){
modCount++;
int numMoved=size-toIndex;
System.arraycopy(elementData, toIndex, elementData, fromIndex, numMoved);
int newSize=size-(toIndex-fromIndex);
for(int i =newSize;i<size;i++)
elementData[i]=null;
size=newSize;
}
/**
*removes from this list all of its elements that are contained in the
*specified collection
*/
@Override
public boolean removeAll(Collection<?> c) {
return batchRemove(c,false);
}
/**
*retains only the elements in this list that are contained in the specified collection
* @param c
* @return
*/
@Override
public boolean retainAll(Collection<?> c) {
return batchRemove(c,true);
}
private boolean batchRemove(Collection<?> c,boolean complement){
final Object[] elementData=this.elementData;
int r=0,w=0;//w中记录要保留的元素
boolean modified=false;
try{
for(;r<size;r++)
if(c.contains(elementData[r])==complement)
elementData[w++]=elementData[r];
}finally{
//如果在赋值的同时发生异常，集合中没有走完的元素赋值给 w
if(r!=size){
System.arraycopy(elementData, r, elementData, w, size-r);
w+=size-r;
}
if(w!=size){
//clear to let GC do its work
for(int i=w;i<size;i++)
elementData[i]=null;
modCount+=size-w;
size=w;
modified=true;
}
}
return modified;
}
/**
* save the state of the ArrayList instance to a stream
* @param s
* @throws java.io.IOException
*/
private void writeObject(ObjectOutputStream s) throws java.io.IOException{
int expectedMoCount=modCount;
s.defaultWriteObject();
//write out size as capacity for behavioural compatibility with clone
s.writeInt(size);
//Write Out all elements in the proper order
for(int i=0;i<size;i++)
s.writeObject(elementData[i]);
if(modCount!=expectedMoCount)
throw new ConcurrentModificationException();
}
/**
* Reconstitute the ArrayList instance from a stream
* @param s
* @throws java.io.IOException
* @throws ClassNotFoundException
*/
private void readObject(ObjectInputStream s) throws java.io.IOException, ClassNotFoundException{
elementData=EMPTY_ELEMENTDATA;
//Read in size,and any hidden stuff
s.defaultReadObject();
//Read in capacity
s.readInt();
if(size>0){
ensureCapacityInteral(size);
//be like clone(),allocate array based upon size not capacity
Object[] a=elementData;
for(int i=0;i<size;i++){
a[i]=s.readObject();
}
}
}
/**
* returns an iterator over the elements in this list in proper sequence
*/
@Override
public Iterator<E> iterator() {
return new Itr();
}
@Override
public ListIterator<E> listIterator() {
// TODO Auto-generated method stub
return null;
}
@Override
public ListIterator<E> listIterator(int index) {
// TODO Auto-generated method stub
return null;
}
/**
* an optimized version of
* @author c_xulei025
*
*/
private class Itr implements Iterator<E>{
int cursor;//index of next elements to return
int lastRet=-1;//index of last elements returned;-1 if no such
int expectedModCount=modCount;
@Override
public boolean hasNext() {
return cursor!=size;
}
@SuppressWarnings("unchecked")
@Override
public E next() {
checkForComodification();
int i=cursor;
if(i>size)
throw new NoSuchElementException();
Object[] elementData=MyArrayList.this.elementData;
if(i>=elementData.length)
throw new ConcurrentModificationException();
cursor=i+1;
return (E) elementData[lastRet=i];
}
@Override
public void remove() {
if(lastRet<0)
throw new IllegalStateException();
checkForComodification();
try{
MyArrayList.this.remove(lastRet);
cursor=lastRet;
lastRet=-1;
expectedModCount=modCount;
}catch(IndexOutOfBoundsException ex){
throw new ConcurrentModificationException();
}
}
final void checkForComodification(){
if(modCount!=expectedModCount)
throw new ConcurrentModificationException();
}
}
private class ListItr extends Itr implements ListIterator<E>{
ListItr(int index){
super();
cursor=index;
}
@Override
public boolean hasPrevious() {
return cursor!=0;
}
@Override
public int nextIndex() {
return cursor;
}
@Override
public int previousIndex() {
return cursor-1;
}
@SuppressWarnings("unchecked")
@Override
public E previous() {
checkForComodification();
int i=cursor-1;
if(i<0)
throw new NoSuchElementException();
Object[] elementData=MyArrayList.this.elementData;
if(i>=elementData.length)
throw new ConcurrentModificationException();
cursor=i;
return (E) elementData[lastRet=i];
}
@Override
public void set(E e) {
if(lastRet<0)
throw new IllegalStateException();
checkForComodification();
try {
MyArrayList.this.set(lastRet, e);
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
@Override
public void add(E e) {
checkForComodification();
try{
int i=cursor;
MyArrayList.this.add(i,e);
cursor=i+1;
lastRet=-1;
expectedModCount=modCount;
}catch(IndexOutOfBoundsException ex){
throw new ConcurrentModificationException();
}
}
}
/**
* returns a view of the portion of this list between the specified
* fromIndex,inclusive and toIndex,exclusive
*
* @param fromIndex
* @param toIndex
* @return
*/
@Override
public List<E> subList(int fromIndex, int toIndex) {
subListRangeCheck(fromIndex, toIndex, size);
return new SubList(this, 0, fromIndex, toIndex);
}
static void subListRangeCheck(int fromIndex, int toIndex, int size) {
if (fromIndex < 0)
throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
if (toIndex > size)
throw new IndexOutOfBoundsException("toIndex = " + toIndex);
if (fromIndex > toIndex)
throw new IllegalArgumentException("fromIndex(" + fromIndex +
") > toIndex(" + toIndex + ")");
}
protected transient int modCount = 0;
private class SubList extends AbstractList<E> implements RandomAccess{
private final AbstractList<E> parent;
private final int parentOffset;
private final int offset;
int size;
SubList(AbstractList<E> parent,
int offset, int fromIndex, int toIndex) {
this.parent = parent;
this.parentOffset = fromIndex;
this.offset = offset + fromIndex;
this.size = toIndex - fromIndex;
this.modCount = MyArrayList.this.modCount;
}
public E set(int index, E e) {
rangeCheck(index);
checkForComodification();
E oldValue = MyArrayList.this.elementData(offset + index);
MyArrayList.this.elementData[offset + index] = e;
return oldValue;
}
public E get(int index) {
rangeCheck(index);
checkForComodification();
return MyArrayList.this.elementData(offset + index);
}
public int size() {
checkForComodification();
return this.size;
}
public void add(int index, E e) {
rangeCheckForAdd(index);
checkForComodification();
parent.add(parentOffset + index, e);
this.size++;
}
public E remove(int index) {
rangeCheck(index);
checkForComodification();
E result = parent.remove(parentOffset + index);
this.size--;
return result;
}
protected void removeRange(int fromIndex, int toIndex) {
checkForComodification();
this.size -= toIndex - fromIndex;
}
public boolean addAll(Collection<? extends E> c) {
return addAll(this.size, c);
}
public boolean addAll(int index, Collection<? extends E> c) {
rangeCheckForAdd(index);
int cSize = c.size();
if (cSize==0)
return false;
checkForComodification();
parent.addAll(parentOffset + index, c);
this.size += cSize;
return true;
}
public Iterator<E> iterator() {
return listIterator();
}
public ListIterator<E> listIterator(final int index) {
checkForComodification();
rangeCheckForAdd(index);
final int offset = this.offset;
return new ListIterator<E>() {
int cursor = index;
int lastRet = -1;
int expectedModCount = MyArrayList.this.modCount;
public boolean hasNext() {
return cursor != SubList.this.size;
}
@SuppressWarnings("unchecked")
public E next() {
checkForComodification();
int i = cursor;
if (i >= SubList.this.size)
throw new NoSuchElementException();
Object[] elementData = MyArrayList.this.elementData;
if (offset + i >= elementData.length)
throw new ConcurrentModificationException();
cursor = i + 1;
return (E) elementData[offset + (lastRet = i)];
}
public boolean hasPrevious() {
return cursor != 0;
}
@SuppressWarnings("unchecked")
public E previous() {
checkForComodification();
int i = cursor - 1;
if (i < 0)
throw new NoSuchElementException();
Object[] elementData = MyArrayList.this.elementData;
if (offset + i >= elementData.length)
throw new ConcurrentModificationException();
cursor = i;
return (E) elementData[offset + (lastRet = i)];
}
public int nextIndex() {
return cursor;
}
public int previousIndex() {
return cursor - 1;
}
public void remove() {
if (lastRet < 0)
throw new IllegalStateException();
checkForComodification();
try {
SubList.this.remove(lastRet);
cursor = lastRet;
lastRet = -1;
expectedModCount = MyArrayList.this.modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
public void set(E e) {
if (lastRet < 0)
throw new IllegalStateException();
checkForComodification();
try {
MyArrayList.this.set(offset + lastRet, e);
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
public void add(E e) {
checkForComodification();
try {
int i = cursor;
SubList.this.add(i, e);
cursor = i + 1;
lastRet = -1;
expectedModCount = MyArrayList.this.modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
final void checkForComodification() {
if (expectedModCount != MyArrayList.this.modCount)
throw new ConcurrentModificationException();
}
};
}
public List<E> subList(int fromIndex, int toIndex) {
subListRangeCheck(fromIndex, toIndex, size);
return new SubList(this, offset, fromIndex, toIndex);
}
private void rangeCheck(int index) {
if (index < 0 || index >= this.size)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
private void rangeCheckForAdd(int index) {
if (index < 0 || index > this.size)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
private String outOfBoundsMsg(int index) {
return "Index: "+index+", Size: "+this.size;
}
private void checkForComodification() {
if (MyArrayList.this.modCount != this.modCount)
throw new ConcurrentModificationException();
}
}
}