package java.util; //util包
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.function.UnaryOperator;
import sun.misc.SharedSecrets;
//继承AbstractList抽象类
//实现List接口；实现RandomAccess接口，做到随机访问，实现Cloneable接口，克隆；实现Serializable接口，序列化（不需要真正实现，只要这样类似声明一下，就知道这个类可以序列化了）
public class ArrayList<E> extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{
private static final long serialVersionUID = 8683452581122892189L; //UID:版本号，序列化和反序列化时候用来对照的
private static final int DEFAULT_CAPACITY = 10; //ArrayList初始容量为10，也可以自己设置
private static final Object[] EMPTY_ELEMENTDATA = {}; //EMPTY_ELEMENTDATA是一个Object的数组，该数组为空；用final修饰，引用无法指向其它对象；static修饰，类加载时就会创建
private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {}; //空的数组，为了和上述区别，因为这是默认初始化时分配的数组
transient Object[] elementData; // 存放数据的Object数组，transient修饰表示不参与序列化
private int size; //数组存放东西的长度
public ArrayList(int initialCapacity) { //第一个带参构造方法，参数是ArrayList数组的大小
if (initialCapacity > 0) { //当传入的参数大于0时（正确）
this.elementData = new Object[initialCapacity]; //新建一个对象数组，并将其赋值给elementData
} else if (initialCapacity == 0) { //当传入的参数等于0时，将一开始创建的EMPTY_ELEMENTDATA数组赋值给elementData
this.elementData = EMPTY_ELEMENTDATA;
} else { //当传入的参数小于0时（不合法），抛出参数错误异常
throw new IllegalArgumentException("Illegal Capacity: "+
initialCapacity);
}
}
public ArrayList() { //默认构造方法，初始为空，DEFAULTCAPACITY_EMPTY_ELEMENTDATA
this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA; //DEFAULTCAPACITY_EMPTY_ELEMENTDATA赋值给elementData
}
public ArrayList(Collection<? extends E> c) { 第三个构造方法，参数是一个Collection，Collection中存放的是E（ArrayList中的元素）或者E的子类
elementData = c.toArray(); //将Collection装换为array，也就是一个数组；
if ((size = elementData.length) != 0) { //如果elementData的长度不为0
// c.toArray might (incorrectly) not return Object[] (see 6260652) ，6260652是jdk bug库中的编号
if (elementData.getClass() != Object[].class) //如果转为Array之后不是Object数组，则要利用Arrays.copyOf转化为Object数组
elementData = Arrays.copyOf(elementData, size, Object[].class);
} else { //如果elementData的长度为0，将其转化为EMPTY_ELEMENTDATA
// replace with empty array.
this.elementData = EMPTY_ELEMENTDATA;
}
}
public void trimToSize() { //截短ArrayList,可能elementData.length > size,那么就可以保留数据部分，将之后的去除，注意，modCount会增加。
modCount++;
if (size < elementData.length) {
elementData = (size == 0)
? EMPTY_ELEMENTDATA
: Arrays.copyOf(elementData, size);
}
}
public void ensureCapacity(int minCapacity) {
int minExpand = (elementData != DEFAULTCAPACITY_EMPTY_ELEMENTDATA)
// any size if not default element table
? 0
// larger than default for default empty table. It's already
// supposed to be at default size.
: DEFAULT_CAPACITY;
if (minCapacity > minExpand) {
ensureExplicitCapacity(minCapacity);
}
}
private static int calculateCapacity(Object[] elementData, int minCapacity) { //计算容量
if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) { //如果数组为空，那么返回初始大小和minCapacity的最大值，也就是说最小为10
return Math.max(DEFAULT_CAPACITY, minCapacity);
}
return minCapacity; //如果数组不为空，那么返回minCapacity
}
private void ensureCapacityInternal(int minCapacity) { //确保数组的大小大于等于minCapacity，这里的minCapcity其实就是数组最后要多大
ensureExplicitCapacity(calculateCapacity(elementData, minCapacity));
}
private void ensureExplicitCapacity(int minCapacity) { //如果minCapacity大于数组的长度，就会执行grow函数增长，并且modCount也会增加，modCount是AbstractList中的成员，标识版本
modCount++;
if (minCapacity - elementData.length > 0)
grow(minCapacity);
}
private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; //最大的长度0x7fffffff - 8
private void grow(int minCapacity) { //扩容操作，
// overflow-conscious code
int oldCapacity = elementData.length; //记录原数组的长度（不是size）
int newCapacity = oldCapacity + (oldCapacity >> 1); //新数组的长度为原数组长度的1.5倍
if (newCapacity - minCapacity < 0) //如果新数组的长度小于最小长度（意味着扩容之后，还是不够），新数组的长度等于最小长度
newCapacity = minCapacity;
if (newCapacity - MAX_ARRAY_SIZE > 0) //如果新数组的长度大于最大容量，新数组的长度转化为整数最大值或者最大容量
newCapacity = hugeCapacity(minCapacity);
// minCapacity is usually close to size, so this is a win:
elementData = Arrays.copyOf(elementData, newCapacity); //最终数组转化为新的长度的数组
}
private static int hugeCapacity(int minCapacity) { //根据最小长度，返回一个数值
if (minCapacity < 0) // overflow //如果最小长度小于0，那么判定为溢出，抛出异常
throw new OutOfMemoryError();
return (minCapacity > MAX_ARRAY_SIZE) ? //如果最小长度大于最大容量，返回整数的最大值，否则返回最大容量
Integer.MAX_VALUE :
MAX_ARRAY_SIZE;
}
public int size() { //返回list的元素个数
return size;
}
public boolean isEmpty() { //判断list中是否存在元素
return size == 0;
}
public boolean contains(Object o) { //判断list中是否存在某个对象
return indexOf(o) >= 0;
}
public int indexOf(Object o) { //返回某个对象在list中的位置，也就是下标
if (o == null) { //如果对象为空，那么找到list中第一个为空的元素，返回其下标
for (int i = 0; i < size; i++)
if (elementData[i]==null)
return i;
} else { //如果对象不为空，那么找到list中第一个等于该对象的元素，返回其下标，这里看似差不多的逻辑，但是不能一起做，因为如果传入的对象为空，会报空指针NullPointerException
for (int i = 0; i < size; i++)
if (o.equals(elementData[i]))
return i;
}
return -1; //如果没找到，那么返回-1，让调用者知道没有
}
public int lastIndexOf(Object o) { //同样寻找某个对象的下标，和indexOf()的区别在于，list中可能有几个同样的该对象，indexOf是从前往后找，并返回第一个，而lastIndexOf()是从后往前找，返回最后一个
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;
}
public Object clone() { //重写了clone()方法，因为调用Object的clone()方法需要实现Cloneable接口，该接口没有任何方法，和Serialization一样，只是标志。并且Object的clone()是protected修饰的，意味着不重写的话其它类可能用不了这个方法
try {
ArrayList<?> v = (ArrayList<?>) super.clone(); //调用clone()方法，并且强转为ArrayList类型，用v接收，v为复制的数组
v.elementData = Arrays.copyOf(elementData, size); //复制原数组中的元素，因为Object的clone()是浅复制，如果存放的是对象的话，这里原数组和复制的数组放的东西都是一样的
v.modCount = 0; //初始化复制的数组的modCount = 0
return v;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError(e);
}
}
public Object[] toArray() { //利用Arrays.copyOf()返回一个数组
return Arrays.copyOf(elementData, size);
}
@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) { //将ArrayList转化为特定的数组，而不一定是Object数组
if (a.length < size)
// Make a new array of a's runtime type, but my contents:
return (T[]) Arrays.copyOf(elementData, size, a.getClass());
System.arraycopy(elementData, 0, a, 0, size);
if (a.length > size)
a[size] = null; //如果传入的数组长度太大，那么需要将size位置为null，以求得数组的size(只有数组中不存在其它null元素的时候管用)
return a;
}
@SuppressWarnings("unchecked") //返回ArrayList特定下标的元素
E elementData(int index) {
return (E) elementData[index];
}
public E get(int index) { //得到ArrayList特定下标的元素，根本上调用了elementData()函数
rangeCheck(index); //判断index的合法性
return elementData(index);
}
public E set(int index, E element) { //设置下标为index的元素，并且该元素为泛型元素，需要和初始设定相同
rangeCheck(index); //检查index的合法性
E oldValue = elementData(index); //保存数组中index上原来的元素
elementData[index] = element; //设置新的值
return oldValue; //返回原来的元素
}
//add()方法要注意的是，其实初始的ArrayList的大小为0，如果增加一个元素，那么就会增长到默认大小，也就是10，这是jdk1.8的修改
public boolean add(E e) { //添加一个元素，modCount + 1
ensureCapacityInternal(size + 1); // 确保数组大小足够，其中会执行ensureExplicitCapacity()方法，该方法会增加modCount
elementData[size++] = e; //size之后的空格内存放该元素
return true; //返回true，代表添加正确
}
public void add(int index, E element) { //往特定的index上增加一个元素,modCount + 1
rangeCheckForAdd(index); //检查index的合法性
ensureCapacityInternal(size + 1); // 确保数组大小足够，其中会执行ensureExplicitCapacity()方法，该方法会增加modCount
System.arraycopy(elementData, index, elementData, index + 1,
size - index); //将index及其之后的元素往后移动，腾出位子
elementData[index] = element; //放入该元素
size++; //修改size
}
public E remove(int index) { //删除某个index上的元素，modCount + 1
rangeCheck(index); //检查index的合法性
modCount++; //modCount + 1(删除不需要检查容量问题)
E oldValue = elementData(index); //保存index上的元素
int numMoved = size - index - 1; //计算需要移动的元素个数
if (numMoved > 0) //如果要移动的元素个数大于0，也就是说index不是最后一个
System.arraycopy(elementData, index+1, elementData, index,
numMoved); //移动数组，将后面的往前移动
elementData[--size] = null; // 将最后一个置为空，以待回收
return oldValue; //返回删除的那个元素
}
public boolean remove(Object o) { //删除某个对象,会调用fastRemove(),增加modCount
if (o == null) { //如果该对象为null
for (int index = 0; index < size; index++) //删除第一个为空的对象(防止空指针异常)
if (elementData[index] == null) {
fastRemove(index);
return true;
}
} else { //否则删除第一个该对象
for (int index = 0; index < size; index++)
if (o.equals(elementData[index])) {
fastRemove(index);
return true;
}
}
return false;
}
private void fastRemove(int index) { //删除某个位置上的元素，modCount++，和普通删除一个元素的区别在于不返回删除的元素，并且这个方法是私有方法
modCount++; //增加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
}
public void clear() { //删除所有的元素，modCount++
modCount++;
// clear to let GC do its work
for (int i = 0; i < size; i++) //将数组上size以内的元素都置为null
elementData[i] = null;
size = 0; //更新size
}
public boolean addAll(Collection<? extends E> c) { //增加一个集合中的所有元素，modCount++
Object[] a = c.toArray(); //首先将集合c转化为数组a
int numNew = a.length; //计算数组a的长度
ensureCapacityInternal(size + numNew); // 确保ArrayList的长度够，这里会调用ensureExplicitCapacity(),所以modCount++
System.arraycopy(a, 0, elementData, size, numNew); //将a数组复制到ArrayList的size之后
size += numNew; //更新size
return numNew != 0; //如果a数组的长度为0，返回false，否则返回true
}
public boolean addAll(int index, Collection<? extends E> c) { //将集合c中的元素都插入index之后，和上一个方法的区别在于插入的位置，以及要使用两次System.arraycopy()方法
rangeCheckForAdd(index);
Object[] a = c.toArray();
int numNew = a.length;
ensureCapacityInternal(size + numNew); // Increments modCount
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;
}
protected void removeRange(int fromIndex, int toIndex) { //批量删除
modCount++;
int numMoved = size - toIndex;
System.arraycopy(elementData, toIndex, elementData, fromIndex,
numMoved);
// clear to let GC do its work
int newSize = size - (toIndex-fromIndex);
for (int i = newSize; i < size; i++) {
elementData[i] = null;
}
size = newSize;
}
private void rangeCheck(int index) { //私有方法，index检查
if (index >= size)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
private void rangeCheckForAdd(int index) { //私有方法，index检查，和上一个方法的区别在于多用于add之类的方法中，所以index可以等于size(可以在size位子上增加)，index < 0
if (index > size || index < 0)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
private String outOfBoundsMsg(int index) { //返回一个outOfBounds信息
return "Index: "+index+", Size: "+size;
}
public boolean removeAll(Collection<?> c) { //删除集合中的所有元素
Objects.requireNonNull(c); //c不能是空
return batchRemove(c, false); //调用batchRemove(),
}
public boolean retainAll(Collection<?> c) { //保留集合中的元素，ArrayList中的其它元素都删除
Objects.requireNonNull(c); //同样，集合c不能是空
return batchRemove(c, true); //调用batchRemove(),
}
private boolean batchRemove(Collection<?> c, boolean complement) { //私有方法，批量删除
final Object[] elementData = this.elementData; //保存数组
int r = 0, w = 0; //两个游标，r遍历数组，w指向最新的一个需要保存的元素
boolean modified = false; //标记是否修改
try {
for (; r < size; r++) //遍历数组，如果c包含此元素，并且传入的complement为true，或者c不包含该元素，并且传入的complement为false，那么就保留，意味着false是删除，true是保留
if (c.contains(elementData[r]) == complement)
elementData[w++] = elementData[r];
} finally {
// Preserve behavioral compatibility with AbstractCollection,
// even if c.contains() throws.
if (r != size) { //如果没有遍历完成，也就是说c.contains()抛出了异常，将r之后的复制到w之后，更新w
System.arraycopy(elementData, r,
elementData, w,
size - r);
w += size - r;
}
if (w != size) { //若果w不等于size，这意味着有些东西要被抛弃了
// 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 <tt>ArrayList</tt> instance to a stream (that
* is, serialize it).
*
* @serialData The length of the array backing the <tt>ArrayList</tt>
* instance is emitted (int), followed by all of its elements
* (each an <tt>Object</tt>) in the proper order.
*/
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException{
// Write out element count, and any hidden stuff
int expectedModCount = 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 != expectedModCount) {
throw new ConcurrentModificationException();
}
}
/**
* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
* deserialize it).
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
elementData = EMPTY_ELEMENTDATA;
// Read in size, and any hidden stuff
s.defaultReadObject();
// Read in capacity
s.readInt(); // ignored
if (size > 0) {
// be like clone(), allocate array based upon size not capacity
int capacity = calculateCapacity(elementData, size);
SharedSecrets.getJavaOISAccess().checkArray(s, Object[].class, capacity);
ensureCapacityInternal(size);
Object[] a = elementData;
// Read in all elements in the proper order.
for (int i=0; i<size; i++) {
a[i] = s.readObject();
}
}
}
public ListIterator<E> listIterator(int index) { //返回一个ListItr，以index开头
if (index < 0 || index > size) //检验index
throw new IndexOutOfBoundsException("Index: "+index);
return new ListItr(index);
}
public ListIterator<E> listIterator() { //返回一个ListItr，以0开头
return new ListItr(0);
}
public Iterator<E> iterator() { //返回一个Itr，并且是fail-fast的，意味着数组改变之后会报错
return new Itr();
}
/**
* An optimized version of AbstractList.Itr
*/
private class Itr implements Iterator<E> { //定义一个内部类Itr，实现了迭代器接口
int cursor; // 下一个要返回的元素下标
int lastRet = -1; // index of last element returned; -1 if no such
int expectedModCount = modCount; //记录下modCount
Itr() {}
public boolean hasNext() { //判断是否存在下一个
return cursor != size; //curse(下一个元素的下标)等于size，意味着没有了下一个元素
}
@SuppressWarnings("unchecked")
public E next() { //得到下一个元素
checkForComodification(); //检查modCount，如果和创建迭代器时候的modCount不同，那么就会报错
int i = cursor; // 保存下一个元素的下标
if (i >= size) //如果下一个返回值大于等于size，抛出异常
throw new NoSuchElementException();
Object[] elementData = ArrayList.this.elementData; //得到数组，因为是内部类，所以要加ArrayList
if (i >= elementData.length) //如果i大于等于数组的长度，同样抛出异常
throw new ConcurrentModificationException();
cursor = i + 1; //更新cursor
return (E) elementData[lastRet = i]; //返回curse下标的元素，并且更新lastRet
}
public void remove() { //删除操作
if (lastRet < 0) //如果最后删除的是-1(代表没有迭代过)，抛出错误
throw new IllegalStateException();
checkForComodification(); //检查modCount是否正确
try {
ArrayList.this.remove(lastRet); //删除最后一个修改的元素
cursor = lastRet; //更新cursor
lastRet = -1; //更新lastRet为-1，这意味着不能来连续删除两次
expectedModCount = modCount; //更新expectedModCount，因为删除之后modCount会改变，所以需要用迭代器的remove()删除，这样会更新expectedModCount，否则如果直接删除ArrayList的元素，modCount改变了，expectedModCount又没改变，这样就会报错
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
@Override
@SuppressWarnings("unchecked")
public void forEachRemaining(Consumer<? super E> consumer) {
Objects.requireNonNull(consumer); //
final int size = ArrayList.this.size;
int i = cursor;
if (i >= size) {
return;
}
final Object[] elementData = ArrayList.this.elementData;
if (i >= elementData.length) {
throw new ConcurrentModificationException();
}
while (i != size && modCount == expectedModCount) {
consumer.accept((E) elementData[i++]);
}
// update once at end of iteration to reduce heap write traffic
cursor = i;
lastRet = i - 1;
checkForComodification();
}
final void checkForComodification() { //检查是否ArrayList是否更改
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
}
}
private class ListItr extends Itr implements ListIterator<E> { //定义一个内部类ListItr，继承了Itr，并且实现了ListIterator接口
ListItr(int index) { //构造函数
super();
cursor = index;
}
public boolean hasPrevious() { //判断时候有前一个元素，只要cursor不等于0，就有前面一个元素
return cursor != 0;
}
public int nextIndex() { //返回下一个元素的下标
return cursor;
}
public int previousIndex() { //返回上一个元素的下标
return cursor - 1;
}
@SuppressWarnings("unchecked")
public E previous() { //返回前一个元素
checkForComodification(); //检查modCount是否改变
int i = cursor - 1; //记录前一个位置
if (i < 0)
throw new NoSuchElementException();
Object[] elementData = ArrayList.this.elementData;
if (i >= elementData.length)
throw new ConcurrentModificationException();
cursor = i; //更新cursor
return (E) elementData[lastRet = i]; //返回前一个元素
}
public void set(E e) { //设置最后一个返回元素
if (lastRet < 0)
throw new IllegalStateException();
checkForComodification(); //检查modCount
try {
ArrayList.this.set(lastRet, e); //将最后一个返回的元素更换
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
public void add(E e) { //添加某个元素
checkForComodification(); /检查modCount
try {
int i = cursor;
ArrayList.this.add(i, e); //将当前游标上添加一个元素
cursor = i + 1; //更新cursor
lastRet = -1; //更新最后返回的元素下标为-1(因为添加后序号都会变)
expectedModCount = modCount; //更新 expectedModCount
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
}
public List<E> subList(int fromIndex, int toIndex) { //返回一个子数组
subListRangeCheck(fromIndex, toIndex, size); //参数检查
return new SubList(this, 0, fromIndex, toIndex);
}
static void subListRangeCheck(int fromIndex, int toIndex, int size) { //检查from和to的格式，并且size是否够
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 + ")");
}
private class SubList extends AbstractList<E> implements RandomAccess { //内部类SubList，继承了AbstractList抽象类，本质上并没有创建一个新的数组，如果对sublist做出改变，都会改变原来的数组
private final AbstractList<E> parent; //成员变量，子数组从哪里来
private final int parentOffset; //父数组的偏移
private final int offset; //自身的偏移
int size; //子数组的负载
SubList(AbstractList<E> parent,
int offset, int fromIndex, int toIndex) { //构造函数，参数为一个AbstractList,子数组的头和尾，便偏移
this.parent = parent;
this.parentOffset = fromIndex; //父数组的偏移为fromIndex
this.offset = offset + fromIndex; //子数组的偏移为自己的偏移加上父数组的偏移
this.size = toIndex - fromIndex; //子数组的负载为需要复制的长度
this.modCount = ArrayList.this.modCount; //子数组的modCount等于父数组的modCount
}
public E set(int index, E e) { //将index下标的元素设置为e
rangeCheck(index); //检查index的正确性
checkForComodification(); //检查modCount
E oldValue = ArrayList.this.elementData(offset + index); //记录下原来的元素，其为父数组上第(offeset + index)个元素
ArrayList.this.elementData[offset + index] = e; //更改元素
return oldValue; //返回旧的值
}
public E get(int index) { //获取index下标的元素
rangeCheck(index);
checkForComodification();
return ArrayList.this.elementData(offset + index);
}
public int size() { //返回子数组的负载
checkForComodification();
return this.size;
}
public void add(int index, E e) { //增加一个元素
rangeCheckForAdd(index);
checkForComodification();
parent.add(parentOffset + index, e);
this.modCount = parent.modCount; //更新modCount
this.size++;
}
public E remove(int index) { //删除一个元素
rangeCheck(index);
checkForComodification();
E result = parent.remove(parentOffset + index);
this.modCount = parent.modCount;
this.size--;
return result;
}
protected void removeRange(int fromIndex, int toIndex) {
checkForComodification();
parent.removeRange(parentOffset + fromIndex,
parentOffset + toIndex);
this.modCount = parent.modCount;
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.modCount = parent.modCount;
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 = ArrayList.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 = ArrayList.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 = ArrayList.this.elementData;
if (offset + i >= elementData.length)
throw new ConcurrentModificationException();
cursor = i;
return (E) elementData[offset + (lastRet = i)];
}
@SuppressWarnings("unchecked")
public void forEachRemaining(Consumer<? super E> consumer) {
Objects.requireNonNull(consumer);
final int size = SubList.this.size;
int i = cursor;
if (i >= size) {
return;
}
final Object[] elementData = ArrayList.this.elementData;
if (offset + i >= elementData.length) {
throw new ConcurrentModificationException();
}
while (i != size && modCount == expectedModCount) {
consumer.accept((E) elementData[offset + (i++)]);
}
// update once at end of iteration to reduce heap write traffic
lastRet = cursor = i;
checkForComodification();
}
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 = ArrayList.this.modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
public void set(E e) {
if (lastRet < 0)
throw new IllegalStateException();
checkForComodification();
try {
ArrayList.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 = ArrayList.this.modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
final void checkForComodification() {
if (expectedModCount != ArrayList.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 (ArrayList.this.modCount != this.modCount)
throw new ConcurrentModificationException();
}
public Spliterator<E> spliterator() {
checkForComodification();
return new ArrayListSpliterator<E>(ArrayList.this, offset,
offset + this.size, this.modCount);
}
}
@Override
public void forEach(Consumer<? super E> action) {
Objects.requireNonNull(action);
final int expectedModCount = modCount;
@SuppressWarnings("unchecked")
final E[] elementData = (E[]) this.elementData;
final int size = this.size;
for (int i=0; modCount == expectedModCount && i < size; i++) {
action.accept(elementData[i]);
}
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
}
/**
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
* and <em>fail-fast</em> {@link Spliterator} over the elements in this
* list.
*
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
* {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
* Overriding implementations should document the reporting of additional
* characteristic values.
*
* @return a {@code Spliterator} over the elements in this list
* @since 1.8
*/
@Override
public Spliterator<E> spliterator() {
return new ArrayListSpliterator<>(this, 0, -1, 0);
}
/** Index-based split-by-two, lazily initialized Spliterator */
static final class ArrayListSpliterator<E> implements Spliterator<E> {
/*
* If ArrayLists were immutable, or structurally immutable (no
* adds, removes, etc), we could implement their spliterators
* with Arrays.spliterator. Instead we detect as much
* interference during traversal as practical without
* sacrificing much performance. We rely primarily on
* modCounts. These are not guaranteed to detect concurrency
* violations, and are sometimes overly conservative about
* within-thread interference, but detect enough problems to
* be worthwhile in practice. To carry this out, we (1) lazily
* initialize fence and expectedModCount until the latest
* point that we need to commit to the state we are checking
* against; thus improving precision. (This doesn't apply to
* SubLists, that create spliterators with current non-lazy
* values). (2) We perform only a single
* ConcurrentModificationException check at the end of forEach
* (the most performance-sensitive method). When using forEach
* (as opposed to iterators), we can normally only detect
* interference after actions, not before. Further
* CME-triggering checks apply to all other possible
* violations of assumptions for example null or too-small
* elementData array given its size(), that could only have
* occurred due to interference. This allows the inner loop
* of forEach to run without any further checks, and
* simplifies lambda-resolution. While this does entail a
* number of checks, note that in the common case of
* list.stream().forEach(a), no checks or other computation
* occur anywhere other than inside forEach itself. The other
* less-often-used methods cannot take advantage of most of
* these streamlinings.
*/
private final ArrayList<E> list;
private int index; // current index, modified on advance/split
private int fence; // -1 until used; then one past last index
private int expectedModCount; // initialized when fence set
/** Create new spliterator covering the given range */
ArrayListSpliterator(ArrayList<E> list, int origin, int fence,
int expectedModCount) {
this.list = list; // OK if null unless traversed
this.index = origin;
this.fence = fence;
this.expectedModCount = expectedModCount;
}
private int getFence() { // initialize fence to size on first use
int hi; // (a specialized variant appears in method forEach)
ArrayList<E> lst;
if ((hi = fence) < 0) {
if ((lst = list) == null)
hi = fence = 0;
else {
expectedModCount = lst.modCount;
hi = fence = lst.size;
}
}
return hi;
}
public ArrayListSpliterator<E> trySplit() {
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
return (lo >= mid) ? null : // divide range in half unless too small
new ArrayListSpliterator<E>(list, lo, index = mid,
expectedModCount);
}
public boolean tryAdvance(Consumer<? super E> action) {
if (action == null)
throw new NullPointerException();
int hi = getFence(), i = index;
if (i < hi) {
index = i + 1;
@SuppressWarnings("unchecked") E e = (E)list.elementData[i];
action.accept(e);
if (list.modCount != expectedModCount)
throw new ConcurrentModificationException();
return true;
}
return false;
}
public void forEachRemaining(Consumer<? super E> action) {
int i, hi, mc; // hoist accesses and checks from loop
ArrayList<E> lst; Object[] a;
if (action == null)
throw new NullPointerException();
if ((lst = list) != null && (a = lst.elementData) != null) {
if ((hi = fence) < 0) {
mc = lst.modCount;
hi = lst.size;
}
else
mc = expectedModCount;
if ((i = index) >= 0 && (index = hi) <= a.length) {
for (; i < hi; ++i) {
@SuppressWarnings("unchecked") E e = (E) a[i];
action.accept(e);
}
if (lst.modCount == mc)
return;
}
}
throw new ConcurrentModificationException();
}
public long estimateSize() {
return (long) (getFence() - index);
}
public int characteristics() {
return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
}
}
@Override
public boolean removeIf(Predicate<? super E> filter) {
Objects.requireNonNull(filter);
// figure out which elements are to be removed
// any exception thrown from the filter predicate at this stage
// will leave the collection unmodified
int removeCount = 0;
final BitSet removeSet = new BitSet(size);
final int expectedModCount = modCount;
final int size = this.size;
for (int i=0; modCount == expectedModCount && i < size; i++) {
@SuppressWarnings("unchecked")
final E element = (E) elementData[i];
if (filter.test(element)) {
removeSet.set(i);
removeCount++;
}
}
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
// shift surviving elements left over the spaces left by removed elements
final boolean anyToRemove = removeCount > 0;
if (anyToRemove) {
final int newSize = size - removeCount;
for (int i=0, j=0; (i < size) && (j < newSize); i++, j++) {
i = removeSet.nextClearBit(i);
elementData[j] = elementData[i];
}
for (int k=newSize; k < size; k++) {
elementData[k] = null; // Let gc do its work
}
this.size = newSize;
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
modCount++;
}
return anyToRemove;
}
@Override
@SuppressWarnings("unchecked")
public void replaceAll(UnaryOperator<E> operator) {
Objects.requireNonNull(operator);
final int expectedModCount = modCount;
final int size = this.size;
for (int i=0; modCount == expectedModCount && i < size; i++) {
elementData[i] = operator.apply((E) elementData[i]);
}
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
modCount++;
}
@Override
@SuppressWarnings("unchecked")
public void sort(Comparator<? super E> c) {
final int expectedModCount = modCount;
Arrays.sort((E[]) elementData, 0, size, c);
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
modCount++;
}
}
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