java源碼筆記-----AbstractList

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注:代碼中的注釋是我的個人理解，如果有誤還請指出。

AbstractList

add操作將元素添加到列表末尾。

    public boolean add(E e) {        add(size(), e);//size()        return true;    }

 

remove操作將指定元素移除列表，通過Iterator的remove方法實現。

public boolean remove(Object o) {        Iterator<E> it = iterator();        if (o==null) {            while (it.hasNext()) {                if (it.next()==null) {                    it.remove();//調用iterator的remove方法                    return true;                }            }        } else {            while (it.hasNext()) {                if (o.equals(it.next())) {                    it.remove();                    return true;                }            }        }        return false;    }/*==========Iterator的remove方法============*//*This method can be called only once per call to {@link #next}.*//*此方法只能在next()方法調用後調用,因為噹噹前指標指向的記憶體中沒有元素時會拋出IllegalStateException*/? default void remove() {        throw new UnsupportedOperationException("remove");    }

 

clear操作通過調用iterator的remove移除列表中的所有元素

 public void clear() {        Iterator<E> it = iterator();        while (it.hasNext()) {            it.next();//先調用next            it.remove();//再移除        }    }

AbstractList.Itr

next()

     public E next() {            checkForComodification();            try {                int i = cursor;//擷取指標                E next = get(i);//擷取指標對應的元素                lastRet = i;//最近調用過next()的元素的index                cursor = i + 1;//指標右移                return next;            } catch (IndexOutOfBoundsException e) {                checkForComodification();                throw new NoSuchElementException();            }        }

 

remove()

?

    public void remove() {            if (lastRet < 0)                throw new IllegalStateException();            checkForComodification();?            try {                AbstractList.this.remove(lastRet);//移除上一次next()或者previous()的元素,列表後面的元素依次左移                if (lastRet < cursor)//如果lastRet小於cursor則說明是next()                    cursor--;//指標左移                lastRet = -1;//重設為-1                expectedModCount = modCount;            } catch (IndexOutOfBoundsException e) {                throw new ConcurrentModificationException();            }        }

 

AbstractList.ListItr

previous()

public E previous() {            checkForComodification();            try {                int i = cursor - 1;//擷取當前指標的上一個元素的index                E previous = get(i);//擷取該元素                lastRet = cursor = i;//cursor指標左移，將lastRet設定為i                return previous;            } catch (IndexOutOfBoundsException e) {                checkForComodification();                throw new NoSuchElementException();            }        }

 

 

add()

    public void add(E e) {            checkForComodification();?            try {                int i = cursor;//擷取當前指標所處的位置                AbstractList.this.add(i, e);//插入到i處                lastRet = -1;                cursor = i + 1;//指標右移，以保持指標所指的元素不變                expectedModCount = modCount;            } catch (IndexOutOfBoundsException ex) {                throw new ConcurrentModificationException();            }        }

 

java源碼筆記-----AbstractList