package java.util;
public abstract class AbstractList<E> extends AbstractCollection<E> implements List<E> {
protected AbstractList() {
}
/**
* 添加元素方法
*/
public boolean add(E e) {
add(size(), e);
return true;
}
/**
* 获取元素的抽象方法
*/
abstract public E get(int index);
/**
* 根据下标设置元素的方法
*/
public E set(int index, E element) {
throw new UnsupportedOperationException();
}
/**
* 根据下标添加元素的方法
*/
public void add(int index, E element) {
throw new UnsupportedOperationException();
}
/**
* 根据下标删除元素的方法
*/
public E remove(int index) {
throw new UnsupportedOperationException();
}
// Search Operations
/**
* 返回列表中某个元素第一次出现的索引位置的方法
*/
public int indexOf(Object o) {
ListIterator<E> e = listIterator();
if (o==null) {
while (e.hasNext())
if (e.next()==null)
return e.previousIndex();
} else {
while (e.hasNext())
if (o.equals(e.next()))
return e.previousIndex();
}
return -1;
}
/**
*返回列表中某个元素最后一次出现的索引位置的方法
*/
public int lastIndexOf(Object o) {
ListIterator<E> e = listIterator(size());
if (o==null) {
while (e.hasPrevious())
if (e.previous()==null)
return e.nextIndex();
} else {
while (e.hasPrevious())
if (o.equals(e.previous()))
return e.nextIndex();
}
return -1;
}
/**
* 清除列表中的所有元素
*/
public void clear() {
removeRange(0, size());
}
/**
* 从指定位置开始将Collection中的元素按迭代顺序加入到列表中
*/
public boolean addAll(int index, Collection<? extends E> c) {
boolean modified = false;
Iterator<? extends E> e = c.iterator();
while (e.hasNext()) {
add(index++, e.next());
modified = true;
}
return modified;
}
/**
* 返回内部实现的迭代器类Itr
*/
public Iterator<E> iterator() {
return new Itr();
}
/**
*继承ListIterator类的方法
*/
public ListIterator<E> listIterator() {
return listIterator(0);
}
/**
* 继承ListIterator类的方法
*/
public ListIterator<E> listIterator(final int index) {
if (index<0 || index>size())
throw new IndexOutOfBoundsException("Index: "+index);
return new ListItr(index);
}
/**
* 私有的内部类，实现了自己的Itertor
*/
private class Itr implements Iterator<E> {
/**
*调用next方法返回的元素索引值
*/
int cursor = 0;
/**
* 调用next方法或者previous方法时返回的索引值，当调用deleted方法时该值重新置-1 */
int lastRet = -1;
/**
* 列表的修改次数
*/
int expectedModCount = modCount;
public boolean hasNext() {
return cursor != size();
}
public E next() {
checkForComodification();
try {
E next = get(cursor);
lastRet = cursor++;
return next;
} catch (IndexOutOfBoundsException e) {
checkForComodification();
throw new NoSuchElementException();
}
}
public void remove() {
if (lastRet == -1)
throw new IllegalStateException();
checkForComodification();
try {
AbstractList.this.remove(lastRet);
if (lastRet < cursor)
cursor--;
lastRet = -1;
expectedModCount = modCount;
} catch (IndexOutOfBoundsException e) {
throw new ConcurrentModificationException();
}
}
final void checkForComodification() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
}
}
/**
* 私有的内部类，实现了自己的列表迭代器类
*/
private class ListItr extends Itr implements ListIterator<E> {
ListItr(int index) {
cursor = index;
}
public boolean hasPrevious() {
return cursor != 0;
}
public E previous() {
checkForComodification();
try {
int i = cursor - 1;
E previous = get(i);
lastRet = cursor = i;
return previous;
} catch (IndexOutOfBoundsException e) {
checkForComodification();
throw new NoSuchElementException();
}
}
public int nextIndex() {
return cursor;
}
public int previousIndex() {
return cursor-1;
}
public void set(E e) {
if (lastRet == -1)
throw new IllegalStateException();
checkForComodification();
try {
AbstractList.this.set(lastRet, e);
expectedModCount = modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
public void add(E e) {
checkForComodification();
try {
AbstractList.this.add(cursor++, e);
lastRet = -1;
expectedModCount = modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
}
/**
* 返回指定位置的列表视图
*/
public List<E> subList(int fromIndex, int toIndex) {
return (this instanceof RandomAccess ?
new RandomAccessSubList<E>(this, fromIndex, toIndex) :
new SubList<E>(this, fromIndex, toIndex));
}
/**
* 比较的方法
*/
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof List))
return false;
ListIterator<E> e1 = listIterator();
ListIterator e2 = ((List) o).listIterator();
while(e1.hasNext() && e2.hasNext()) {
E o1 = e1.next();
Object o2 = e2.next();
if (!(o1==null ? o2==null : o1.equals(o2)))
return false;
}
return !(e1.hasNext() || e2.hasNext());
}
/**
* 重写的hashcode方法
*/
public int hashCode() {
int hashCode = 1;
Iterator<E> i = iterator();
while (i.hasNext()) {
E obj = i.next();
hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode());
}
return hashCode;
}
/**
*删除指定区间元素的方法
*/
protected void removeRange(int fromIndex, int toIndex) {
ListIterator<E> it = listIterator(fromIndex);
for (int i=0, n=toIndex-fromIndex; i<n; i++) {
it.next();
it.remove();
}
}
/**
* 列表结构被修改的次数，比如列表的size变化或者打乱列表使得迭代结果不正确
*/
protected transient int modCount = 0;
}
/**
* 子列表类
*/
class SubList<E> extends AbstractList<E> {
private AbstractList<E> l;
private int offset;
private int size;
private int expectedModCount;
SubList(AbstractList<E> list, int fromIndex, int toIndex) {
if (fromIndex < 0)
throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
if (toIndex > list.size())
throw new IndexOutOfBoundsException("toIndex = " + toIndex);
if (fromIndex > toIndex)
throw new IllegalArgumentException("fromIndex(" + fromIndex +
") > toIndex(" + toIndex + ")");
l = list;
offset = fromIndex;
size = toIndex - fromIndex;
expectedModCount = l.modCount;
}
public E set(int index, E element) {
rangeCheck(index);
checkForComodification();
return l.set(index+offset, element);
}
public E get(int index) {
rangeCheck(index);
checkForComodification();
return l.get(index+offset);
}
public int size() {
checkForComodification();
return size;
}
public void add(int index, E element) {
if (index<0 || index>size)
throw new IndexOutOfBoundsException();
checkForComodification();
l.add(index+offset, element);
expectedModCount = l.modCount;
size++;
modCount++;
}
public E remove(int index) {
rangeCheck(index);
checkForComodification();
E result = l.remove(index+offset);
expectedModCount = l.modCount;
size--;
modCount++;
return result;
}
protected void removeRange(int fromIndex, int toIndex) {
checkForComodification();
l.removeRange(fromIndex+offset, toIndex+offset);
expectedModCount = l.modCount;
size -= (toIndex-fromIndex);
modCount++;
}
public boolean addAll(Collection<? extends E> c) {
return addAll(size, c);
}
public boolean addAll(int index, Collection<? extends E> c) {
if (index<0 || index>size)
throw new IndexOutOfBoundsException(
"Index: "+index+", Size: "+size);
int cSize = c.size();
if (cSize==0)
return false;
checkForComodification();
l.addAll(offset+index, c);
expectedModCount = l.modCount;
size += cSize;
modCount++;
return true;
}
public Iterator<E> iterator() {
return listIterator();
}
public ListIterator<E> listIterator(final int index) {
checkForComodification();
if (index<0 || index>size)
throw new IndexOutOfBoundsException(
"Index: "+index+", Size: "+size);
return new ListIterator<E>() {
private ListIterator<E> i = l.listIterator(index+offset);
public boolean hasNext() {
return nextIndex() < size;
}
public E next() {
if (hasNext())
return i.next();
else
throw new NoSuchElementException();
}
public boolean hasPrevious() {
return previousIndex() >= 0;
}
public E previous() {
if (hasPrevious())
return i.previous();
else
throw new NoSuchElementException();
}
public int nextIndex() {
return i.nextIndex() - offset;
}
public int previousIndex() {
return i.previousIndex() - offset;
}
public void remove() {
i.remove();
expectedModCount = l.modCount;
size--;
modCount++;
}
public void set(E e) {
i.set(e);
}
public void add(E e) {
i.add(e);
expectedModCount = l.modCount;
size++;
modCount++;
}
};
}
public List<E> subList(int fromIndex, int toIndex) {
return new SubList<E>(this, fromIndex, toIndex);
}
private void rangeCheck(int index) {
if (index<0 || index>=size)
throw new IndexOutOfBoundsException("Index: "+index+
",Size: "+size);
}
private void checkForComodification() {
if (l.modCount != expectedModCount)
throw new ConcurrentModificationException();
}
}
/**
* 具有随机访问性质的子列表类
*/
class RandomAccessSubList<E> extends SubList<E> implements RandomAccess {
RandomAccessSubList(AbstractList<E> list, int fromIndex, int toIndex) {
super(list, fromIndex, toIndex);
}
public List<E> subList(int fromIndex, int toIndex) {
return new RandomAccessSubList<E>(this, fromIndex, toIndex);
}
}
