所在包
package java.util;继续AbstractCollection抽象类
实现List接口
public abstract class AbstractList<E> extends AbstractCollection<E> implements List<E>{
// 内部代码下面讲解
}空构造器
protected AbstractList() {
}添加元素，在尾部添加新的元素
/* @throws UnsupportedOperationException if the {@code add} operation
* is not supported by this list
* @throws ClassCastException if the class of the specified element
* prevents it from being added to this list
* @throws NullPointerException if the specified element is null and this
* list does not permit null elements
* @throws IllegalArgumentException if some property of this element
* prevents it from being added to this list
*/
public boolean add(E e) {
add(size(), e);
return true;
}获取指定index位置元素
/ * @throws IndexOutOfBoundsException {@inheritDoc}
*/
abstract public E get(int index);更新index位置元素
/** @throws UnsupportedOperationException {@inheritDoc}
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
public E set(int index, E element) {
throw new UnsupportedOperationException();
}
index位置插入元素
/** @throws UnsupportedOperationException {@inheritDoc}
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
public void add(int index, E element) {
throw new UnsupportedOperationException();
}删除inde位置元素
/** @throws UnsupportedOperationException {@inheritDoc}
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
public E remove(int index) {
throw new UnsupportedOperationException();
}
利用迭代器，查找元素首次出现的下标
不存在返回-1
/** @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public int indexOf(Object o) {
ListIterator<E> it = listIterator();
if (o==null) {
while (it.hasNext())
if (it.next()==null)
return it.previousIndex();
} else {
while (it.hasNext())
if (o.equals(it.next()))
return it.previousIndex();
}
return -1;
}利用迭代器，查找到元素最后一次出现的下标
不存在返回-1
/** @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public int lastIndexOf(Object o) {
ListIterator<E> it = listIterator(size());// 从这个位置构建迭代器
if (o==null) {
while (it.hasPrevious())// 向前查找
if (it.previous()==null)
return it.nextIndex();
} else {
while (it.hasPrevious())
if (o.equals(it.previous()))
return it.nextIndex();
}
return -1;
}清空元素
/** @throws UnsupportedOperationException if the {@code clear} operation
* is not supported by this list
*/
public void clear() {
removeRange(0, size());
}从集合c中index位置开始，讲元素插入到当前集合中
* @throws UnsupportedOperationException {@inheritDoc}
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
public boolean addAll(int index, Collection<? extends E> c) {
rangeCheckForAdd(index);
boolean modified = false;
for (E e : c) {
add(index++, e);
modified = true;
}
return modified;
}获取迭代器
public Iterator<E> iterator() {
return new Itr();
}获取迭代器
public ListIterator<E> listIterator() {
return listIterator(0);
}
指定index开始获取迭代器
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
public ListIterator<E> listIterator(final int index) {
rangeCheckForAdd(index);
return new ListItr(index);
}内部类，实现Iterator迭代器
private class Itr implements Iterator<E> {
/**
* 当前运行的位置
*/
int cursor = 0;
/**
* Index of element returned by most recent call to next or
* previous. Reset to -1 if this element is deleted by a call
* to remove.
*/
int lastRet = -1;
/**
* 修改次数
*/
int expectedModCount = modCount;
// 是否结束
public boolean hasNext() {
return cursor != size();
}
// 当前元素值
public E next() {
checkForComodification();// 检查是否合法id
try {
int i = cursor;
E next = get(i);
lastRet = i;
cursor = i + 1;
return next;
} catch (IndexOutOfBoundsException e) {
checkForComodification();
throw new NoSuchElementException();
}
}
// 删除当前元素
public void remove() {
if (lastRet < 0)
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();
}
}ListItr 继承Itr 实现ListIterator
增加前驱遍历
// 从当前index开始构建迭代器
private class ListItr extends Itr implements ListIterator<E> {
// 设置开始位置
ListItr(int index) {
cursor = index;
}
// 是否有前驱
public boolean hasPrevious() {
return cursor != 0;
}
// 前驱节点值
public E previous() {
checkForComodification();
try {
int i = cursor - 1;// 更新-1
E previous = get(i);
lastRet = cursor = i;
return previous;
} catch (IndexOutOfBoundsException e) {
checkForComodification();
throw new NoSuchElementException();
}
}
// 后继下标
public int nextIndex() {
return cursor;
}
// 前驱下标
public int previousIndex() {
return cursor-1;
}
// 尾部更新元素
public void set(E e) {
if (lastRet < 0)
throw new IllegalStateException();
checkForComodification();
try {
AbstractList.this.set(lastRet, e);
expectedModCount = modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
// 当前位置更新元素
public void add(E e) {
checkForComodification();
try {
int i = cursor;
AbstractList.this.add(i, e);
lastRet = -1;
cursor = i + 1;
expectedModCount = modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
}
}获取子数组
/** @throws IndexOutOfBoundsException if an endpoint index value is out of range
* { (fromIndex < 0 || toIndex > size)}
* @throws IllegalArgumentException if the endpoint indices are out of order
* { (fromIndex > toIndex)}
*/
public List<E> subList(int fromIndex, int toIndex) {
return (this instanceof RandomAccess ?
new RandomAccessSubList<>(this, fromIndex, toIndex) :
new SubList<>(this, fromIndex, toIndex));
}重写equals方法
public boolean equals(Object o) {
if (o == this)// 当前对象
return true;
if (!(o instanceof List))// 不是子对象
return false;
ListIterator<E> e1 = listIterator();// 构建迭代器
ListIterator e2 = ((List) o).listIterator();
while (e1.hasNext() && e2.hasNext()) {
E o1 = e1.next();
Object o2 = e2.next();// 比较每个元素
if (!(o1==null ? o2==null : o1.equals(o2)))
return false;
}
return !(e1.hasNext() || e2.hasNext());
}计算hashcode
public int hashCode() {
int hashCode = 1;
for (E e : this)
hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
return hashCode;
}迭代的方式
hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());删除区间元素
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();
}
}下标检查
protected transient int modCount = 0;
private void rangeCheckForAdd(int index) {
if (index < 0 || index > size())
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}输出信息
private String outOfBoundsMsg(int index) {
return "Index: "+index+", Size: "+size();
}在AbstractList.java文件中还实现了subList的操作，由于这个也是list，其操作和list的一样，贴下代码
class SubList<E> extends AbstractList<E> {
private final AbstractList<E> l;
private final int offset;
private int size;
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;
this.modCount = 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) {
rangeCheckForAdd(index);
checkForComodification();
l.add(index+offset, element);
this.modCount = l.modCount;
size++;
}
public E remove(int index) {
rangeCheck(index);
checkForComodification();
E result = l.remove(index+offset);
this.modCount = l.modCount;
size--;
return result;
}
protected void removeRange(int fromIndex, int toIndex) {
checkForComodification();
l.removeRange(fromIndex+offset, toIndex+offset);
this.modCount = l.modCount;
size -= (toIndex-fromIndex);
}
public boolean addAll(Collection<? extends E> c) {
return addAll(size, c);
}
public boolean addAll(int index, Collection<? extends E> c) {
rangeCheckForAdd(index);
int cSize = c.size();
if (cSize==0)
return false;
checkForComodification();
l.addAll(offset+index, c);
this.modCount = l.modCount;
size += cSize;
return true;
}
public Iterator<E> iterator() {
return listIterator();
}
public ListIterator<E> listIterator(final int index) {
checkForComodification();
rangeCheckForAdd(index);
return new ListIterator<E>() {
private final 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();
SubList.this.modCount = l.modCount;
size--;
}
public void set(E e) {
i.set(e);
}
public void add(E e) {
i.add(e);
SubList.this.modCount = l.modCount;
size++;
}
};
}
public List<E> subList(int fromIndex, int toIndex) {
return new SubList<>(this, fromIndex, toIndex);
}
private void rangeCheck(int index) {
if (index < 0 || index >= size)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
private void rangeCheckForAdd(int index) {
if (index < 0 || index > size)
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
private String outOfBoundsMsg(int index) {
return "Index: "+index+", Size: "+size;
}
private void checkForComodification() {
if (this.modCount != l.modCount)
throw new ConcurrentModificationException();
}
}
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<>(this, fromIndex, toIndex);
}
}时间： 2024-10-13 11:50:03