LinkedList源码

Posted 2022-01-08 yaowen

   

public class TestLinkedList 
    @Test
    public void testQuery() 

         LinkedList1<Integer> list=new LinkedList1<Integer>();
         list.add(22);
         list.add(66);
         list.addFirst(77);
         list.addLast(99);
         Iterator i = list.iterator();//就有了所有的元素了。
         while(i.hasNext()) 
             System.out.println(i.next());
         
        
         
        A a = new A(1, "1");// [email protected]
        A b = new A(2, "2");// [email protected]
        LinkedList1<A> list1 = new LinkedList1<A>(Arrays.asList(a, b));// [[email protected], [email protected]]
        LinkedList1 list2 = (LinkedList1) list1.clone();// [[email protected], [email protected]]。
                                                        // first，last等属性地址不一样了。里面的元素传递的还是地址。
        System.out.println(list1);// [[email protected], [email protected]]
        System.out.println(list2);// [[email protected], [email protected]]
        a.k = 4;
        a.s = "ff";
        System.out.println(list1);// [[email protected], [email protected]],里面的a改变了。
        System.out.println(list2);// [[email protected], [email protected]],里面的a改变了。
        Object[] ss = list1.toArray();// [[email protected], [email protected]]
        System.out.println(ss);
        a.k = 8;
        a.s = "刚刚";
        System.out.println(ss);// ss里面的a也改变了。
        
        
        Object[] ss1 = list1.toArray(new A[] new A(3,"3"),new A(33,"33"),new A(444,"444"),new A(555,"555"));
        //list的元素 + null + a数组后面的元素，
        
        A c = new A(9,"d");
        A d = new A(0,"pp");
        A f = new A(89,"89");
        A g = new A(90,"90");
        list1.add(c);
        list1.add(d);
        list1.add(f);
        list1.add(null);
        list1.add(g);
        LLSpliterator ll = (LLSpliterator) list1.spliterator();
        Spliterator kk = ll.trySplit();
        ((Spliterator) ll).forEachRemaining(new Consumer<A>() 
            public void accept(A a) 
                System.out.println(a);
            
        );
        kk.forEachRemaining(new Consumer<A>() 
            public void accept(A a) 
                System.out.println(a);
            
        );
    


class A 
    public String s;
    public int k;
    A(int i, String b) 
        this.s = b;
        this.k = i;
    

public class LinkedList1<E> extends AbstractSequentialList1<E> implements List<E>, Deque<E>, Cloneable, 
java.io.Serializable
    transient int size = 0;//结点个数
    transient Node<E> first;
    transient Node<E> last;
    public LinkedList1() 
    
    public LinkedList1(Collection<? extends E> c) 
        this();
        addAll(c);
    

    private void linkFirst(E e) //头部加一个元素
        final Node<E> f = first;//first有可能是null
        final Node<E> newNode = new Node<>(null, e, f);
        first = newNode;
        if (f == null)
            last = newNode;
        else
            f.prev = newNode;
        size++;
        modCount++;
    

    void linkLast(E e) 
        final Node<E> l = last;//last有可能是null
        final Node<E> newNode = new Node<>(l, e, null);
        last = newNode;
        if (l == null)
            first = newNode;
        else
            l.next = newNode;
        size++;
        modCount++;
    

    void linkBefore(E e, Node<E> succ) 
        assert succ != null;
        final Node<E> pred = succ.prev;//succ不为null，前驱有可能是null
        final Node<E> newNode = new Node<>(pred, e, succ);
        succ.prev = newNode;
        if (pred == null)//succ是头结点
            first = newNode;//新节点是头结点
        else
            pred.next = newNode;
        size++;
        modCount++;
    

    //删除头结点
    private E unlinkFirst(Node<E> f) 
        assert f == first && f != null;
        final E element = f.item;//要return出去的
        final Node<E> next = f.next;//要修改前驱结点的
        f.item = null;
        f.next = null; // help GC
        first = next;
        if (next == null)
            last = null;
        else
            next.prev = null;
        size--;
        modCount++;
        return element;
    

    //删除尾结点
    private E unlinkLast(Node<E> l) 
        assert l == last && l != null;
        final E element = l.item;//要return出去的
        final Node<E> prev = l.prev;//要修改后继结点的
        l.item = null;
        l.prev = null; // help GC
        last = prev;
        if (prev == null)
            first = null;
        else
            prev.next = null;
        size--;
        modCount++;
        return element;
    

    //删除X结点
    E unlink(Node<E> x) 
        assert x != null;
        final E element = x.item;
        final Node<E> next = x.next;//next可能是null
        final Node<E> prev = x.prev;//prev可能是null

        if (prev == null) 
            first = next;
         else 
            prev.next = next;
            x.prev = null;
        

        if (next == null) 
            last = prev;
         else 
            next.prev = prev;
            x.next = null;
        

        x.item = null;
        size--;
        modCount++;
        return element;
    

    public E getFirst() 
        final Node<E> f = first;
        if (f == null)
            throw new NoSuchElementException();
        return f.item;
    

    public E getLast() 
        final Node<E> l = last;
        if (l == null)
            throw new NoSuchElementException();
        return l.item;
    

    public E removeFirst() 
        final Node<E> f = first;
        if (f == null)
            throw new NoSuchElementException();
        return unlinkFirst(f);
    

    public E removeLast() 
        final Node<E> l = last;
        if (l == null)
            throw new NoSuchElementException();
        return unlinkLast(l);
    

    public void addFirst(E e) 
        linkFirst(e);
    

    public void addLast(E e) 
        linkLast(e);
    

    public boolean contains(Object o) 
        return indexOf(o) != -1;
    

    public int size() 
        return size;
    

    public boolean add(E e) 
        linkLast(e);
        return true;
    

    public boolean remove(Object o) 
        if (o == null) 
            for (Node<E> x = first; x != null; x = x.next) 
                if (x.item == null) 
                    unlink(x);
                    return true;
                
            
         else 
            for (Node<E> x = first; x != null; x = x.next) 
                if (o.equals(x.item)) 
                    unlink(x);
                    return true;
                
            
        
        return false;
    

    //尾部添加，添加时候集合不能修改
    public boolean addAll(Collection<? extends E> c) 
        return addAll(size, c);
    

    public boolean addAll(int index, Collection<? extends E> c) 
        checkPositionIndex(index);
        Object[] a = c.toArray();//集合转换为数组
        int numNew = a.length;
        if (numNew == 0)
            return false;
        Node<E> pred, succ;//pred和succ之间添加
        if (index == size) //尾部添加
            succ = null;
            pred = last;
         else 
            succ = node(index);//中间结点succ后添加
            pred = succ.prev;
        
        //先把元素全部加到pred的后面
        for (Object o : a) 
            E e = (E) o;
            Node<E> newNode = new Node<>(pred, e, null);
            if (pred == null)
                first = newNode;
            else
                pred.next = newNode;
            pred = newNode;
        
        //最后加上succ结点
        if (succ == null) 
            last = pred;
         else 
            pred.next = succ;
            succ.prev = pred;
        
        size += numNew;
        modCount++;
        return true;
    

    public void clear() 
        for (Node<E> x = first; x != null; ) 
            Node<E> next = x.next;
            x.item = null;
            x.next = null;
            x.prev = null;//每个结点的3个属性全部清空
            x = next;
        
        first = last = null;
        size = 0;
        modCount++;
    

    public E get(int index) 
        checkElementIndex(index);
        return node(index).item;
    

    public E set(int index, E element) 
        checkElementIndex(index);
        Node<E> x = node(index);
        E oldVal = x.item;
        x.item = element;
        return oldVal;
    

    public void add(int index, E element) 
        checkPositionIndex(index);

        if (index == size)
            linkLast(element);
        else
            linkBefore(element, node(index));
    

    public E remove(int index) 
        checkElementIndex(index);
        return unlink(node(index));
    

    private boolean isElementIndex(int index) 
        return index >= 0 && index < size;
    

    private boolean isPositionIndex(int index) 
        return index >= 0 && index <= size;
    

    private String outOfBoundsMsg(int index) 
        return "Index: "+index+", Size: "+size;
    

    private void checkElementIndex(int index) 
        if (!isElementIndex(index))
            throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
    

    private void checkPositionIndex(int index) 
        if (!isPositionIndex(index))
            throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
    

    //双向链表：只能从前找或者从后找。二分。下标为index，第index+1位置的元素。
    Node<E> node(int index) 
        assert isElementIndex(index);

        if (index < (size >> 1)) 
            Node<E> x = first;
            for (int i = 0; i < index; i++)
                x = x.next;
            return x;
         else 
            Node<E> x = last;
            for (int i = size - 1; i > index; i--)
                x = x.prev;
            return x;
        
    

    // Search Operations
    public int indexOf(Object o) //从前向后找，第一个遇到的。
        int index = 0;
        if (o == null) 
            for (Node<E> x = first; x != null; x = x.next) 
                if (x.item == null)
                    return index;
                index++;
            
         else 
            for (Node<E> x = first; x != null; x = x.next) 
                if (o.equals(x.item))
                    return index;
                index++;
            
        
        return -1;
    

    //从后面开始查找
    public int lastIndexOf(Object o) 
        int index = size;
        if (o == null) 
            for (Node<E> x = last; x != null; x = x.prev) 
                index--;
                if (x.item == null)
                    return index;
            
         else 
            for (Node<E> x = last; x != null; x = x.prev) 
                index--;
                if (o.equals(x.item))
                    return index;
            
        
        return -1;
    

    //返回头结点元素，但不清空
    public E peek() 
        final Node<E> f = first;
        return (f == null) ? null : f.item;
    

    public E element() 
        return getFirst();
    

    //返回并清除头结点
    public E poll() 
        final Node<E> f = first;
        return (f == null) ? null : unlinkFirst(f);
    

    public E remove() 
        return removeFirst();
    

    //尾部添加
    public boolean offer(E e) 
        return add(e);
    

    public boolean offerFirst(E e) 
        addFirst(e);
        return true;
    

    public boolean offerLast(E e) 
        addLast(e);
        return true;
    

    public E peekFirst() 
        final Node<E> f = first;
        return (f == null) ? null : f.item;
     

    public E peekLast() 
        final Node<E> l = last;
        return (l == null) ? null : l.item;
    

    public E pollFirst() 
        final Node<E> f = first;
        return (f == null) ? null : unlinkFirst(f);
    

    public E pollLast() 
        final Node<E> l = last;
        return (l == null) ? null : unlinkLast(l);
    

    public void push(E e) 
        addFirst(e);
    

    public E pop() 
        return removeFirst();
    

    public boolean removeFirstOccurrence(Object o) //从前往后找
        return remove(o);
    

    public boolean removeLastOccurrence(Object o) //从后往前找
        if (o == null) 
            for (Node<E> x = last; x != null; x = x.prev) 
                if (x.item == null) 
                    unlink(x);
                    return true;
                
            
         else 
            for (Node<E> x = last; x != null; x = x.prev) 
                if (o.equals(x.item)) 
                    unlink(x);
                    return true;
                
            
        
        return false;
    

    public ListIterator<E> listIterator(int index) 
        checkPositionIndex(index);
        return new ListItr(index);//从index开始遍历,new之后就有了所有的元素了。
    

    private class ListItr implements ListIterator<E> 
        private Node<E> next;//还没有访问的元素，
        private int nextIndex;//还没有访问的索引，
        private Node<E> lastReturned;//遍历时候的元素
        private int expectedModCount = modCount;

        ListItr(int index) 
            assert isPositionIndex(index);
            next = (index == size) ? null : node(index);//下一个访问的元素
            nextIndex = index;//下一个访问的索引
        

        public boolean hasNext() 
            return nextIndex < size;
        

        public E next() //遍历一次
            checkForComodification();
            if (!hasNext())
                throw new NoSuchElementException();
            lastReturned = next;
            next = next.next;//修改next
            nextIndex++;//修改下一个索引
            return lastReturned.item;//返回元素
        

        public boolean hasPrevious() 
            return nextIndex > 0;//就可以减一
        

        public E previous() //前面一个
            checkForComodification();
            if (!hasPrevious())
                throw new NoSuchElementException();
            //next == null表示刚刚访问的元素是last元素，
            lastReturned = next = (next == null) ? last : next.prev;
            nextIndex--;
            return lastReturned.item;
        

        public int nextIndex() 
            return nextIndex;
        

        public int previousIndex() 
            return nextIndex - 1;
        

        public void remove() 
            checkForComodification();
            if (lastReturned == null)
                throw new IllegalStateException();

            Node<E> lastNext = lastReturned.next;
            unlink(lastReturned);
            if (next == lastReturned)
                next = lastNext;
            else
                nextIndex--;
            lastReturned = null;
            expectedModCount++;
        

        public void set(E e) 
            if (lastReturned == null)
                throw new IllegalStateException();
            checkForComodification();
            lastReturned.item = e;
        

        public void add(E e) 
            checkForComodification();
            lastReturned = null;
            if (next == null)
                linkLast(e);
            else
                linkBefore(e, next);
            nextIndex++;
            expectedModCount++;
        

        public void forEachRemaining(Consumer<? super E> action) 
            Objects.requireNonNull(action);
            //父List被修改了，就快速失败。
            while (modCount == expectedModCount && nextIndex < size) 
                action.accept(next.item);
                lastReturned = next;
                next = next.next;
                nextIndex++;
            
            checkForComodification();
        

        final void checkForComodification() 
            if (modCount != expectedModCount)//父List被修改了，就快速失败。
                throw new ConcurrentModificationException();
        
    

    private static class Node<E> 
        E item;
        Node<E> next;
        Node<E> prev;

        Node(Node<E> prev, E element, Node<E> next) 
            this.item = element;
            this.next = next;
            this.prev = prev;
        
    

    public Iterator<E> descendingIterator() 
        return new DescendingIterator();
    

    //从后往前遍历器
    private class DescendingIterator implements Iterator<E> 
        private final ListItr itr = new ListItr(size());
        public boolean hasNext() 
            return itr.hasPrevious();
        
        public E next() 
            return itr.previous();
        
        public void remove() 
            itr.remove();
        
    

    private LinkedList1<E> superClone() 
        try 
            return (LinkedList1<E>) super.clone();//浅拷贝，地址复制拷贝。
         catch (CloneNotSupportedException e) 
            throw new InternalError(e);
        
    

    //深度拷贝重新建立一个。浅拷贝就是属性地址全是一样的，深拷贝是属性地址不一样。如果元素是对象，对象的地址还是一样。
    public Object clone() 
        LinkedList1<E> clone = superClone();//[[email protected], [email protected]]
        System.out.println(this.first);//@24fcf36f
        System.out.println(this.last);//@10feca44
        System.out.println(clone.first);//@24fcf36f
        System.out.println(clone.last);//@10feca44 。    浅拷贝属性地址是一样的。
        clone.first = clone.last = null;
        clone.size = 0;
        clone.modCount = 0;
        for (Node<E> x = first; x != null; x = x.next)
            clone.add(x.item);//item也是地址
        System.out.println(clone.first);//@3fb1549b
        System.out.println(clone.last);//@ea6147e 。  深拷贝属性地址不是一样的。里面的元素还是地址传递，所以是一样的。
        return clone;//[[email protected], [email protected]]
    

    public Object[] toArray() 
        Object[] result = new Object[size];
        int i = 0;
        for (Node<E> x = first; x != null; x = x.next)
            result[i++] = x.item;//item传递的是地址，
        return result;
    

    public <T> T[] toArray(T[] a) 
        if (a.length < size)//a的长度小，把a变成list的长度，并全部置为null。然后把list的元素赋值进去，返回的就是list的数组
            a = (T[])java.lang.reflect.Array.newInstance(a.getClass().getComponentType(), size);
        int i = 0;
        Object[] result = a;
        for (Node<E> x = first; x != null; x = x.next)
            result[i++] = x.item;
        if (a.length > size)//list的元素 + null + a数组后面的元素，
            a[size] = null;
        return a;
    

    private static final long serialVersionUID = 876323262645176354L;

    public void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException 
        // Write out any hidden serialization magic
        s.defaultWriteObject();
        // Write out size
        s.writeInt(size);
        // Write out all elements in the proper order.
        for (Node<E> x = first; x != null; x = x.next)
            s.writeObject(x.item);
    

    @SuppressWarnings("unchecked")
    public void readObject(java.io.ObjectInputStream s)
        throws java.io.IOException, ClassNotFoundException 
        // Read in any hidden serialization magic
        s.defaultReadObject();

        // Read in size
        int size = s.readInt();

        // Read in all elements in the proper order.
        for (int i = 0; i < size; i++)
            linkLast((E)s.readObject());
    

    @Override
    public Spliterator<E> spliterator() 
        return new LLSpliterator<E>(this, -1, 0);
    

    /** A customized variant of Spliterators.IteratorSpliterator */
    static final class LLSpliterator<E> implements Spliterator<E> 
        static final int BATCH_UNIT = 1 << 10;  // 批处理数组大小增量,  1024
        static final int MAX_BATCH = 1 << 25;  // 最大批处理数组大小,  33554432
        final LinkedList1<E> list;  
        Node<E> current;      // 当前遍历节点
        int est;              //尾节点，初始值为-1，
        int expectedModCount; // initialized when est set
        int batch;            // 拆分的批量大小

        LLSpliterator(LinkedList1<E> list, int est, int expectedModCount) 
            this.list = list;
            this.est = est;//尾节点，初始值为-1，
            this.expectedModCount = expectedModCount;
        

        final int getEst() 
            int s; // force initialization
            final LinkedList1<E> lst;
            if ((s = est) < 0) //est为-1
                if ((lst = list) == null)
                    s = est = 0;
                else 
                    expectedModCount = lst.modCount;
                    current = lst.first;
                    s = est = lst.size;
                
            
            return s;
        

        public long estimateSize()  return (long) getEst(); 

        public Spliterator<E> trySplit() 
            Node<E> p;
            int s = getEst();//7
            if (s > 1 && (p = current) != null) 
                int n = batch + BATCH_UNIT;//1024+batch
                if (n > s)
                    n = s;
                if (n > MAX_BATCH)//33554432，最大大小，
                    n = MAX_BATCH;//n是s,1024+batch,33554432中最小的。
                Object[] a = new Object[n];
                int j = 0;
                do  
                    a[j++] = p.item; 
                 while ((p = p.next) != null && j < n);//到达list结尾  或者  把s填满，
                current = p;//null
                batch = j;//7
                est = s - j;//0
                return Spliterators.spliterator(a, 0, j, Spliterator.ORDERED);//返回ArraySpliterator
            
            return null;
        

        public void forEachRemaining(Consumer<? super E> action) 
            Node<E> p; int n;
            if (action == null) throw new NullPointerException();
            if ((n = getEst()) > 0 && (p = current) != null) 
                current = null;
                est = 0;
                do 
                    E e = p.item;
                    p = p.next;
                    action.accept(e);
                 while (p != null && --n > 0);
            
            if (list.modCount != expectedModCount)
                throw new ConcurrentModificationException();
        

        public boolean tryAdvance(Consumer<? super E> action) 
            Node<E> p;
            if (action == null) throw new NullPointerException();
            if (getEst() > 0 && (p = current) != null) 
                --est;
                E e = p.item;
                current = p.next;
                action.accept(e);
                if (list.modCount != expectedModCount)
                    throw new ConcurrentModificationException();
                return true;
            
            return false;
        

        public int characteristics() 
            return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
        
    

public abstract class AbstractSequentialList1<E> extends AbstractList<E> 
    protected AbstractSequentialList1() 
    

    public E get(int index) 
        try 
            return listIterator(index).next();
         catch (NoSuchElementException exc) 
            throw new IndexOutOfBoundsException("Index: "+index);
        
    

    public E set(int index, E element) 
        try 
            ListIterator<E> e = listIterator(index);
            E oldVal = e.next();
            e.set(element);
            return oldVal;
         catch (NoSuchElementException exc) 
            throw new IndexOutOfBoundsException("Index: "+index);
        
    

    public void add(int index, E element) 
        try 
            listIterator(index).add(element);
         catch (NoSuchElementException exc) 
            throw new IndexOutOfBoundsException("Index: "+index);
        
    

    public E remove(int index) 
        try 
            ListIterator<E> e = listIterator(index);
            E outCast = e.next();
            e.remove();
            return outCast;
         catch (NoSuchElementException exc) 
            throw new IndexOutOfBoundsException("Index: "+index);
        
    


    // Bulk Operations
    public boolean addAll(int index, Collection<? extends E> c) 
        try 
            boolean modified = false;
            ListIterator<E> e1 = listIterator(index);
            Iterator<? extends E> e2 = c.iterator();
            while (e2.hasNext()) 
                e1.add(e2.next());
                modified = true;
            
            return modified;
         catch (NoSuchElementException exc) 
            throw new IndexOutOfBoundsException("Index: "+index);
        
    


    // Iterators
    public Iterator<E> iterator() 
        return listIterator();
    
    public abstract ListIterator<E> listIterator(int index);