4、集合--ArrayList和LinkedList、AbstractSequentialList源码
ArrayList源码
public class ArrayList<E> extends AbstractList<E> implements List<E>, RandomAccess, Cloneable, java.io.Serializable { private static final long serialVersionUID = 8683452581122892189L; /** * Default initial capacity. */ private static final int DEFAULT_CAPACITY = 10; /** * Shared empty array instance used for empty instances. */ private static final Object[] EMPTY_ELEMENTDATA = {}; private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {}; transient Object[] elementData; // non-private to simplify nested class access private int size; public ArrayList(int initialCapacity) { if (initialCapacity > 0) { this.elementData = new Object[initialCapacity]; } else if (initialCapacity == 0) { this.elementData = EMPTY_ELEMENTDATA; } else { throw new IllegalArgumentException("Illegal Capacity: "+ initialCapacity); } } /** * Constructs an empty list with an initial capacity of ten. */ public ArrayList() { this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA; } public ArrayList(Collection<? extends E> c) { elementData = c.toArray(); if ((size = elementData.length) != 0) { // c.toArray might (incorrectly) not return Object[] (see 6260652) if (elementData.getClass() != Object[].class) elementData = Arrays.copyOf(elementData, size, Object[].class); } else { // replace with empty array. this.elementData = EMPTY_ELEMENTDATA; } } public void trimToSize() { 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 void ensureCapacityInternal(int minCapacity) { if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) { minCapacity = Math.max(DEFAULT_CAPACITY, minCapacity); } ensureExplicitCapacity(minCapacity); } private void ensureExplicitCapacity(int minCapacity) { modCount++; // overflow-conscious code if (minCapacity - elementData.length > 0) grow(minCapacity); } private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; private void grow(int minCapacity) { // overflow-conscious code int oldCapacity = elementData.length; int newCapacity = oldCapacity + (oldCapacity >> 1); if (newCapacity - minCapacity < 0) newCapacity = minCapacity; if (newCapacity - MAX_ARRAY_SIZE > 0) newCapacity = hugeCapacity(minCapacity); // minCapacity is usually close to size, so this is a win: elementData = Arrays.copyOf(elementData, newCapacity); } private static int hugeCapacity(int minCapacity) { if (minCapacity < 0) // overflow throw new OutOfMemoryError(); return (minCapacity > MAX_ARRAY_SIZE) ? Integer.MAX_VALUE : MAX_ARRAY_SIZE; } /** * Returns the number of elements in this list. * * @return the number of elements in this list */ public int size() { return size; } /** * Returns <tt>true</tt> if this list contains no elements. * * @return <tt>true</tt> if this list contains no elements */ public boolean isEmpty() { return size == 0; } public boolean contains(Object o) { return indexOf(o) >= 0; } public int indexOf(Object o) { if (o == null) { for (int i = 0; i < size; i++) if (elementData[i]==null) return i; } else { for (int i = 0; i < size; i++) if (o.equals(elementData[i])) return i; } return -1; } public int lastIndexOf(Object o) { 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() { try { ArrayList<?> v = (ArrayList<?>) super.clone(); v.elementData = Arrays.copyOf(elementData, size); v.modCount = 0; return v; } catch (CloneNotSupportedException e) { // this shouldn't happen, since we are Cloneable throw new InternalError(e); } } public Object[] toArray() { return Arrays.copyOf(elementData, size); } @SuppressWarnings("unchecked") public <T> T[] toArray(T[] a) { 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; return a; } // Positional Access Operations @SuppressWarnings("unchecked") E elementData(int index) { return (E) elementData[index]; } public E get(int index) { rangeCheck(index); return elementData(index); } public E set(int index, E element) { rangeCheck(index); E oldValue = elementData(index); elementData[index] = element; return oldValue; } public boolean add(E e) { ensureCapacityInternal(size + 1); // Increments modCount!! elementData[size++] = e; return true; } public void add(int index, E element) { rangeCheckForAdd(index); ensureCapacityInternal(size + 1); // Increments modCount!! System.arraycopy(elementData, index, elementData, index + 1, size - index); elementData[index] = element; size++; } public E remove(int index) { rangeCheck(index); modCount++; E oldValue = elementData(index); 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 return oldValue; } public boolean remove(Object o) { if (o == null) { for (int index = 0; index < size; index++) if (elementData[index] == null) { fastRemove(index); return true; } } else { for (int index = 0; index < size; index++) if (o.equals(elementData[index])) { fastRemove(index); return true; } } return false; } private void fastRemove(int index) { 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() { modCount++; // clear to let GC do its work for (int i = 0; i < size; i++) elementData[i] = null; size = 0; } public boolean addAll(Collection<? extends E> c) { Object[] a = c.toArray(); int numNew = a.length; ensureCapacityInternal(size + numNew); // Increments modCount System.arraycopy(a, 0, elementData, size, numNew); size += numNew; return numNew != 0; } public boolean addAll(int index, Collection<? extends E> c) { 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) { 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; } /** * Checks if the given index is in range. If not, throws an appropriate * runtime exception. This method does *not* check if the index is * negative: It is always used immediately prior to an array access, * which throws an ArrayIndexOutOfBoundsException if index is negative. */ private void rangeCheck(int index) { if (index >= size) throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); } /** * A version of rangeCheck used by add and addAll. */ private void rangeCheckForAdd(int index) { if (index > size || index < 0) throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); } /** * Constructs an IndexOutOfBoundsException detail message. * Of the many possible refactorings of the error handling code, * this "outlining" performs best with both server and client VMs. */ private String outOfBoundsMsg(int index) { return "Index: "+index+", Size: "+size; } public boolean removeAll(Collection<?> c) { Objects.requireNonNull(c); return batchRemove(c, false); } public boolean retainAll(Collection<?> c) { Objects.requireNonNull(c); return batchRemove(c, true); } private boolean batchRemove(Collection<?> c, boolean complement) { final Object[] elementData = this.elementData; int r = 0, w = 0; boolean modified = false; try { for (; r < size; r++) if (c.contains(elementData[r]) == complement) elementData[w++] = elementData[r]; } finally { // Preserve behavioral compatibility with AbstractCollection, // even if c.contains() throws. if (r != size) { System.arraycopy(elementData, r, elementData, w, size - r); w += size - r; } if (w != size) { // 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; } 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 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) { if (index < 0 || index > size) throw new IndexOutOfBoundsException("Index: "+index); return new ListItr(index); } public ListIterator<E> listIterator() { return new ListItr(0); } public Iterator<E> iterator() { return new Itr(); } /** * An optimized version of AbstractList.Itr */ private class Itr implements Iterator<E> { int cursor; // index of next element to return int lastRet = -1; // index of last element returned; -1 if no such int expectedModCount = modCount; public boolean hasNext() { return cursor != size; } @SuppressWarnings("unchecked") public E next() { checkForComodification(); int i = cursor; if (i >= size) throw new NoSuchElementException(); Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) throw new ConcurrentModificationException(); cursor = i + 1; return (E) elementData[lastRet = i]; } public void remove() { if (lastRet < 0) throw new IllegalStateException(); checkForComodification(); try { ArrayList.this.remove(lastRet); cursor = lastRet; lastRet = -1; expectedModCount = modCount; } 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() { if (modCount != expectedModCount) throw new ConcurrentModificationException(); } } /** * An optimized version of AbstractList.ListItr */ private class ListItr extends Itr implements ListIterator<E> { ListItr(int index) { super(); cursor = index; } public boolean hasPrevious() { return cursor != 0; } public int nextIndex() { return cursor; } public int previousIndex() { return cursor - 1; } @SuppressWarnings("unchecked") public E previous() { checkForComodification(); int i = cursor - 1; if (i < 0) throw new NoSuchElementException(); Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) throw new ConcurrentModificationException(); cursor = i; return (E) elementData[lastRet = i]; } public void set(E e) { if (lastRet < 0) throw new IllegalStateException(); checkForComodification(); try { ArrayList.this.set(lastRet, e); } catch (IndexOutOfBoundsException ex) { throw new ConcurrentModificationException(); } } public void add(E e) { checkForComodification(); try { int i = cursor; ArrayList.this.add(i, e); cursor = i + 1; lastRet = -1; expectedModCount = modCount; } catch (IndexOutOfBoundsException ex) { throw new ConcurrentModificationException(); } } } public List<E> subList(int fromIndex, int toIndex) { subListRangeCheck(fromIndex, toIndex, size); return new SubList(this, 0, fromIndex, toIndex); } static void subListRangeCheck(int fromIndex, int toIndex, int size) { 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 { private final AbstractList<E> parent; private final int parentOffset; private final int offset; int size; SubList(AbstractList<E> parent, int offset, int fromIndex, int toIndex) { this.parent = parent; this.parentOffset = fromIndex; this.offset = offset + fromIndex; this.size = toIndex - fromIndex; this.modCount = ArrayList.this.modCount; } public E set(int index, E e) { rangeCheck(index); checkForComodification(); E oldValue = ArrayList.this.elementData(offset + index); ArrayList.this.elementData[offset + index] = e; return oldValue; } public E get(int index) { rangeCheck(index); checkForComodification(); return ArrayList.this.elementData(offset + index); } public int size() { checkForComodification(); return this.size; } public void add(int index, E e) { rangeCheckForAdd(index); checkForComodification(); parent.add(parentOffset + index, e); this.modCount = parent.modCount; this.size++; } public E remove(int index) { 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(); } } @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> { 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++; } }
LinkedList源码
public class LinkedList<E> extends AbstractSequentialList<E> implements List<E>, Deque<E>, Cloneable, java.io.Serializable { transient int size = 0; transient Node<E> first; transient Node<E> last; /** * Constructs an empty list. */ public LinkedList() { } public LinkedList(Collection<? extends E> c) { this(); addAll(c); } /** * Links e as first element. */ private void linkFirst(E e) { final Node<E> f = first; final Node<E> newNode = new Node<>(null, e, f); first = newNode; if (f == null) last = newNode; else f.prev = newNode; size++; modCount++; } /** * Links e as last element. */ void linkLast(E e) { final Node<E> l = last; final Node<E> newNode = new Node<>(l, e, null); last = newNode; if (l == null) first = newNode; else l.next = newNode; size++; modCount++; } /** * Inserts element e before non-null Node succ. */ void linkBefore(E e, Node<E> succ) { // assert succ != null; final Node<E> pred = succ.prev; final Node<E> newNode = new Node<>(pred, e, succ); succ.prev = newNode; if (pred == null) first = newNode; else pred.next = newNode; size++; modCount++; } /** * Unlinks non-null first node f. */ private E unlinkFirst(Node<E> f) { // assert f == first && f != null; final E element = f.item; final Node<E> next = f.next; f.item = null; f.next = null; // help GC first = next; if (next == null) last = null; else next.prev = null; size--; modCount++; return element; } /** * Unlinks non-null last node l. */ private E unlinkLast(Node<E> l) { // assert l == last && l != null; final E element = l.item; final Node<E> prev = l.prev; l.item = null; l.prev = null; // help GC last = prev; if (prev == null) first = null; else prev.next = null; size--; modCount++; return element; } /** * Unlinks non-null node x. */ E unlink(Node<E> x) { // assert x != null; final E element = x.item; final Node<E> next = x.next; final Node<E> prev = x.prev; 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; } /** * Returns the first element in this list. * * @return the first element in this list * @throws NoSuchElementException if this list is empty */ public E getFirst() { final Node<E> f = first; if (f == null) throw new NoSuchElementException(); return f.item; } /** * Returns the last element in this list. * * @return the last element in this list * @throws NoSuchElementException if this list is empty */ public E getLast() { final Node<E> l = last; if (l == null) throw new NoSuchElementException(); return l.item; } /** * Removes and returns the first element from this list. * * @return the first element from this list * @throws NoSuchElementException if this list is empty */ public E removeFirst() { final Node<E> f = first; if (f == null) throw new NoSuchElementException(); return unlinkFirst(f); } /** * Removes and returns the last element from this list. * * @return the last element from this list * @throws NoSuchElementException if this list is empty */ public E removeLast() { final Node<E> l = last; if (l == null) throw new NoSuchElementException(); return unlinkLast(l); } /** * Inserts the specified element at the beginning of this list. * * @param e the element to add */ 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; } 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(); int numNew = a.length; if (numNew == 0) return false; Node<E> pred, succ; if (index == size) { succ = null; pred = last; } else { succ = node(index); pred = succ.prev; } for (Object o : a) { @SuppressWarnings("unchecked") E e = (E) o; Node<E> newNode = new Node<>(pred, e, null); if (pred == null) first = newNode; else pred.next = newNode; pred = newNode; } if (succ == null) { last = pred; } else { pred.next = succ; succ.prev = pred; } size += numNew; modCount++; return true; } /** * Removes all of the elements from this list. * The list will be empty after this call returns. */ public void clear() { // Clearing all of the links between nodes is "unnecessary", but: // - helps a generational GC if the discarded nodes inhabit // more than one generation // - is sure to free memory even if there is a reachable Iterator for (Node<E> x = first; x != null; ) { Node<E> next = x.next; x.item = null; x.next = null; x.prev = null; 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)); } /** * Tells if the argument is the index of an existing element. */ 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)); } /** * Returns the (non-null) Node at the specified element index. */ 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; } } public int indexOf(Object o) { 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; } 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; } public E peek() { final Node<E> f = first; return (f == null) ? null : f.item; } public E element() { return getFirst(); } public E poll() { final Node<E> f = first; return (f == null) ? null : unlinkFirst(f); } public E remove() { return removeFirst(); } 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) { return remove(o); } public boolean removeLastOccurrence(Object o) { 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); } private class ListItr implements ListIterator<E> { private Node<E> lastReturned; private Node<E> next; private int nextIndex; private int expectedModCount = modCount; ListItr(int index) { // assert isPositionIndex(index); next = (index == size) ? null : node(index); nextIndex = index; } public boolean hasNext() { return nextIndex < size; } public E next() { checkForComodification(); if (!hasNext()) throw new NoSuchElementException(); lastReturned = next; next = next.next; nextIndex++; return lastReturned.item; } public boolean hasPrevious() { return nextIndex > 0; } public E previous() { checkForComodification(); if (!hasPrevious()) throw new NoSuchElementException(); 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); while (modCount == expectedModCount && nextIndex < size) { action.accept(next.item); lastReturned = next; next = next.next; nextIndex++; } checkForComodification(); } final void checkForComodification() { if (modCount != expectedModCount) 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; } } /** * @since 1.6 */ public Iterator<E> descendingIterator() { return new DescendingIterator(); } /** * Adapter to provide descending iterators via ListItr.previous */ 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(); } } @SuppressWarnings("unchecked") private LinkedList<E> superClone() { try { return (LinkedList<E>) super.clone(); } catch (CloneNotSupportedException e) { throw new InternalError(e); } } public Object clone() { LinkedList<E> clone = superClone(); // Put clone into "virgin" state clone.first = clone.last = null; clone.size = 0; clone.modCount = 0; // Initialize clone with our elements for (Node<E> x = first; x != null; x = x.next) clone.add(x.item); return clone; } 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; return result; } @SuppressWarnings("unchecked") public <T> T[] toArray(T[] a) { if (a.length < size) 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) a[size] = null; return a; } private static final long serialVersionUID = 876323262645176354L; private 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); } /** * Reconstitutes this {@code LinkedList} instance from a stream * (that is, deserializes it). */ @SuppressWarnings("unchecked") private 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; // batch array size increment static final int MAX_BATCH = 1 << 25; // max batch array size; final LinkedList<E> list; // null OK unless traversed Node<E> current; // current node; null until initialized int est; // size estimate; -1 until first needed int expectedModCount; // initialized when est set int batch; // batch size for splits LLSpliterator(LinkedList<E> list, int est, int expectedModCount) { this.list = list; this.est = est; this.expectedModCount = expectedModCount; } final int getEst() { int s; // force initialization final LinkedList<E> lst; if ((s = est) < 0) { 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(); if (s > 1 && (p = current) != null) { int n = batch + BATCH_UNIT; if (n > s) n = s; if (n > MAX_BATCH) n = MAX_BATCH; Object[] a = new Object[n]; int j = 0; do { a[j++] = p.item; } while ((p = p.next) != null && j < n); current = p; batch = j; est = s - j; return Spliterators.spliterator(a, 0, j, Spliterator.ORDERED); } 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; } } }
AbstractSequentialList源码
public abstract class AbstractSequentialList<E> extends AbstractList<E> { protected AbstractSequentialList() { } 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); } } 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); } } public Iterator<E> iterator() { return listIterator(); } public abstract ListIterator<E> listIterator(int index); }
