diff --git a/src/share/classes/java/util/LinkedList.java b/src/share/classes/java/util/LinkedList.java
index 6b7636c8f81d2046f54f5965bdff433ac5bd0c09..24f465179e271cb1112aea3df324ca795485b4c6 100644
--- a/src/share/classes/java/util/LinkedList.java
+++ b/src/share/classes/java/util/LinkedList.java
@@ -26,22 +26,22 @@
package java.util;
/**
- * Linked list implementation of the List interface. Implements all
+ * Linked list implementation of the {@code List} interface. Implements all
* optional list operations, and permits all elements (including
- * null). In addition to implementing the List interface,
- * the LinkedList class provides uniformly named methods to
- * get, remove and insert an element at the
+ * {@code null}). In addition to implementing the {@code List} interface,
+ * the {@code LinkedList} class provides uniformly named methods to
+ * {@code get}, {@code remove} and {@code insert} an element at the
* beginning and end of the list. These operations allow linked lists to be
* used as a stack, {@linkplain Queue queue}, or {@linkplain Deque
- * double-ended queue}.
+ * double-ended queue}.
*
- * The class implements the Deque interface, providing
- * first-in-first-out queue operations for add,
- * poll, along with other stack and deque operations.
+ *
The class implements the {@code Deque} interface, providing
+ * first-in-first-out queue operations for {@code add},
+ * {@code poll}, along with other stack and deque operations.
*
- * All of the operations perform as could be expected for a doubly-linked
+ *
All of the operations perform as could be expected for a doubly-linked
* list. Operations that index into the list will traverse the list from
- * the beginning or the end, whichever is closer to the specified index.
+ * the beginning or the end, whichever is closer to the specified index.
*
*
Note that this implementation is not synchronized.
* If multiple threads access a linked list concurrently, and at least
@@ -58,11 +58,11 @@ package java.util;
* unsynchronized access to the list:
* List list = Collections.synchronizedList(new LinkedList(...));
*
- * The iterators returned by this class's iterator and
- * listIterator methods are fail-fast: if the list is
+ *
The iterators returned by this class's {@code iterator} and
+ * {@code listIterator} methods are fail-fast: if the list is
* structurally modified at any time after the iterator is created, in
- * any way except through the Iterator's own remove or
- * add methods, the iterator will throw a {@link
+ * any way except through the Iterator's own {@code remove} or
+ * {@code add} methods, the iterator will throw a {@link
* ConcurrentModificationException}. Thus, in the face of concurrent
* modification, the iterator fails quickly and cleanly, rather than
* risking arbitrary, non-deterministic behavior at an undetermined
@@ -71,7 +71,7 @@ package java.util;
*
Note that the fail-fast behavior of an iterator cannot be guaranteed
* as it is, generally speaking, impossible to make any hard guarantees in the
* presence of unsynchronized concurrent modification. Fail-fast iterators
- * throw ConcurrentModificationException on a best-effort basis.
+ * throw {@code ConcurrentModificationException} on a best-effort basis.
* Therefore, it would be wrong to write a program that depended on this
* exception for its correctness: the fail-fast behavior of iterators
* should be used only to detect bugs.
@@ -83,7 +83,6 @@ package java.util;
* @author Josh Bloch
* @see List
* @see ArrayList
- * @see Vector
* @since 1.2
* @param the type of elements held in this collection
*/
@@ -92,14 +91,26 @@ public class LinkedList
extends AbstractSequentialList
implements List, Deque, Cloneable, java.io.Serializable
{
- private transient Entry header = new Entry(null, null, null);
- private transient int size = 0;
+ transient int size = 0;
+
+ /**
+ * Pointer to first node.
+ * Invariant: (first == null && last == null) ||
+ * (first.prev == null && first.item != null)
+ */
+ transient Node first;
+
+ /**
+ * Pointer to last node.
+ * Invariant: (first == null && last == null) ||
+ * (last.next == null && last.item != null)
+ */
+ transient Node last;
/**
* Constructs an empty list.
*/
public LinkedList() {
- header.next = header.previous = header;
}
/**
@@ -115,6 +126,119 @@ public class LinkedList
addAll(c);
}
+ /**
+ * Links e as first element.
+ */
+ private void linkFirst(E e) {
+ final Node f = first;
+ final Node 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 l = last;
+ final Node 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 succ) {
+ // assert succ != null;
+ final Node pred = succ.prev;
+ final Node 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 f) {
+ // assert f == first && f != null;
+ final E element = f.item;
+ final Node 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 l) {
+ // assert l == last && l != null;
+ final E element = l.item;
+ final Node 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 x) {
+ // assert x != null;
+ final E element = x.item;
+ final Node next = x.next;
+ final Node 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.
*
@@ -122,10 +246,10 @@ public class LinkedList
* @throws NoSuchElementException if this list is empty
*/
public E getFirst() {
- if (size==0)
+ final Node f = first;
+ if (f == null)
throw new NoSuchElementException();
-
- return header.next.element;
+ return f.item;
}
/**
@@ -135,10 +259,10 @@ public class LinkedList
* @throws NoSuchElementException if this list is empty
*/
public E getLast() {
- if (size==0)
+ final Node l = last;
+ if (l == null)
throw new NoSuchElementException();
-
- return header.previous.element;
+ return l.item;
}
/**
@@ -148,7 +272,10 @@ public class LinkedList
* @throws NoSuchElementException if this list is empty
*/
public E removeFirst() {
- return remove(header.next);
+ final Node f = first;
+ if (f == null)
+ throw new NoSuchElementException();
+ return unlinkFirst(f);
}
/**
@@ -158,7 +285,10 @@ public class LinkedList
* @throws NoSuchElementException if this list is empty
*/
public E removeLast() {
- return remove(header.previous);
+ final Node l = last;
+ if (l == null)
+ throw new NoSuchElementException();
+ return unlinkLast(l);
}
/**
@@ -167,7 +297,7 @@ public class LinkedList
* @param e the element to add
*/
public void addFirst(E e) {
- addBefore(e, header.next);
+ linkFirst(e);
}
/**
@@ -178,17 +308,17 @@ public class LinkedList
* @param e the element to add
*/
public void addLast(E e) {
- addBefore(e, header);
+ linkLast(e);
}
/**
- * Returns true if this list contains the specified element.
- * More formally, returns true if and only if this list contains
- * at least one element e such that
+ * Returns {@code true} if this list contains the specified element.
+ * More formally, returns {@code true} if and only if this list contains
+ * at least one element {@code e} such that
* (o==null ? e==null : o.equals(e)).
*
* @param o element whose presence in this list is to be tested
- * @return true if this list contains the specified element
+ * @return {@code true} if this list contains the specified element
*/
public boolean contains(Object o) {
return indexOf(o) != -1;
@@ -209,10 +339,10 @@ public class LinkedList
* This method is equivalent to {@link #addLast}.
*
* @param e element to be appended to this list
- * @return true (as specified by {@link Collection#add})
+ * @return {@code true} (as specified by {@link Collection#add})
*/
public boolean add(E e) {
- addBefore(e, header);
+ linkLast(e);
return true;
}
@@ -220,27 +350,27 @@ public class LinkedList
* Removes the first occurrence of the specified element from this list,
* if it is present. If this list does not contain the element, it is
* unchanged. More formally, removes the element with the lowest index
- * i such that
+ * {@code i} such that
* (o==null ? get(i)==null : o.equals(get(i)))
- * (if such an element exists). Returns true if this list
+ * (if such an element exists). Returns {@code true} if this list
* contained the specified element (or equivalently, if this list
* changed as a result of the call).
*
* @param o element to be removed from this list, if present
- * @return true if this list contained the specified element
+ * @return {@code true} if this list contained the specified element
*/
public boolean remove(Object o) {
- if (o==null) {
- for (Entry e = header.next; e != header; e = e.next) {
- if (e.element==null) {
- remove(e);
+ if (o == null) {
+ for (Node x = first; x != null; x = x.next) {
+ if (x.item == null) {
+ unlink(x);
return true;
}
}
} else {
- for (Entry e = header.next; e != header; e = e.next) {
- if (o.equals(e.element)) {
- remove(e);
+ for (Node x = first; x != null; x = x.next) {
+ if (o.equals(x.item)) {
+ unlink(x);
return true;
}
}
@@ -257,7 +387,7 @@ public class LinkedList
* this list, and it's nonempty.)
*
* @param c collection containing elements to be added to this list
- * @return true if this list changed as a result of the call
+ * @return {@code true} if this list changed as a result of the call
* @throws NullPointerException if the specified collection is null
*/
public boolean addAll(Collection extends E> c) {
@@ -275,45 +405,66 @@ public class LinkedList
* @param index index at which to insert the first element
* from the specified collection
* @param c collection containing elements to be added to this list
- * @return true if this list changed as a result of the call
+ * @return {@code true} if this list changed as a result of the call
* @throws IndexOutOfBoundsException {@inheritDoc}
* @throws NullPointerException if the specified collection is null
*/
public boolean addAll(int index, Collection extends E> c) {
- if (index < 0 || index > size)
- throw new IndexOutOfBoundsException("Index: "+index+
- ", Size: "+size);
+ checkPositionIndex(index);
+
Object[] a = c.toArray();
int numNew = a.length;
- if (numNew==0)
+ if (numNew == 0)
return false;
- modCount++;
- Entry successor = (index==size ? header : entry(index));
- Entry predecessor = successor.previous;
- for (int i=0; i e = new Entry((E)a[i], successor, predecessor);
- predecessor.next = e;
- predecessor = e;
+ Node 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 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;
}
- successor.previous = predecessor;
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() {
- Entry e = header.next;
- while (e != header) {
- Entry next = e.next;
- e.next = e.previous = null;
- e.element = null;
- e = next;
+ // 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 x = first; x != null; ) {
+ Node next = x.next;
+ x.item = null;
+ x.next = null;
+ x.prev = null;
+ x = next;
}
- header.next = header.previous = header;
+ first = last = null;
size = 0;
modCount++;
}
@@ -329,7 +480,8 @@ public class LinkedList
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
public E get(int index) {
- return entry(index).element;
+ checkElementIndex(index);
+ return node(index).item;
}
/**
@@ -342,9 +494,10 @@ public class LinkedList
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
public E set(int index, E element) {
- Entry e = entry(index);
- E oldVal = e.element;
- e.element = element;
+ checkElementIndex(index);
+ Node x = node(index);
+ E oldVal = x.item;
+ x.item = element;
return oldVal;
}
@@ -358,7 +511,12 @@ public class LinkedList
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
public void add(int index, E element) {
- addBefore(element, (index==size ? header : entry(index)));
+ checkPositionIndex(index);
+
+ if (index == size)
+ linkLast(element);
+ else
+ linkBefore(element, node(index));
}
/**
@@ -371,34 +529,69 @@ public class LinkedList
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
public E remove(int index) {
- return remove(entry(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;
+ }
+
+ /**
+ * Tells if the argument is the index of a valid position for an
+ * iterator or an add operation.
+ */
+ private boolean isPositionIndex(int index) {
+ return index >= 0 && index <= size;
+ }
+
+ /**
+ * 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;
+ }
+
+ 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 indexed entry.
+ * Returns the (non-null) Node at the specified element index.
*/
- private Entry entry(int index) {
- if (index < 0 || index >= size)
- throw new IndexOutOfBoundsException("Index: "+index+
- ", Size: "+size);
- Entry e = header;
+ Node node(int index) {
+ // assert isElementIndex(index);
+
if (index < (size >> 1)) {
- for (int i = 0; i <= index; i++)
- e = e.next;
+ Node x = first;
+ for (int i = 0; i < index; i++)
+ x = x.next;
+ return x;
} else {
- for (int i = size; i > index; i--)
- e = e.previous;
+ Node x = last;
+ for (int i = size - 1; i > index; i--)
+ x = x.prev;
+ return x;
}
- return e;
}
-
// Search Operations
/**
* Returns the index of the first occurrence of the specified element
* in this list, or -1 if this list does not contain the element.
- * More formally, returns the lowest index i such that
+ * More formally, returns the lowest index {@code i} such that
* (o==null ? get(i)==null : o.equals(get(i))),
* or -1 if there is no such index.
*
@@ -408,15 +601,15 @@ public class LinkedList
*/
public int indexOf(Object o) {
int index = 0;
- if (o==null) {
- for (Entry e = header.next; e != header; e = e.next) {
- if (e.element==null)
+ if (o == null) {
+ for (Node x = first; x != null; x = x.next) {
+ if (x.item == null)
return index;
index++;
}
} else {
- for (Entry e = header.next; e != header; e = e.next) {
- if (o.equals(e.element))
+ for (Node x = first; x != null; x = x.next) {
+ if (o.equals(x.item))
return index;
index++;
}
@@ -427,7 +620,7 @@ public class LinkedList
/**
* Returns the index of the last occurrence of the specified element
* in this list, or -1 if this list does not contain the element.
- * More formally, returns the highest index i such that
+ * More formally, returns the highest index {@code i} such that
* (o==null ? get(i)==null : o.equals(get(i))),
* or -1 if there is no such index.
*
@@ -437,16 +630,16 @@ public class LinkedList
*/
public int lastIndexOf(Object o) {
int index = size;
- if (o==null) {
- for (Entry e = header.previous; e != header; e = e.previous) {
+ if (o == null) {
+ for (Node x = last; x != null; x = x.prev) {
index--;
- if (e.element==null)
+ if (x.item == null)
return index;
}
} else {
- for (Entry e = header.previous; e != header; e = e.previous) {
+ for (Node x = last; x != null; x = x.prev) {
index--;
- if (o.equals(e.element))
+ if (o.equals(x.item))
return index;
}
}
@@ -457,17 +650,18 @@ public class LinkedList
/**
* Retrieves, but does not remove, the head (first element) of this list.
- * @return the head of this list, or null if this list is empty
+ *
+ * @return the head of this list, or {@code null} if this list is empty
* @since 1.5
*/
public E peek() {
- if (size==0)
- return null;
- return getFirst();
+ final Node f = first;
+ return (f == null) ? null : f.item;
}
/**
* Retrieves, but does not remove, the head (first element) of this list.
+ *
* @return the head of this list
* @throws NoSuchElementException if this list is empty
* @since 1.5
@@ -477,14 +671,14 @@ public class LinkedList
}
/**
- * Retrieves and removes the head (first element) of this list
- * @return the head of this list, or null if this list is empty
+ * Retrieves and removes the head (first element) of this list.
+ *
+ * @return the head of this list, or {@code null} if this list is empty
* @since 1.5
*/
public E poll() {
- if (size==0)
- return null;
- return removeFirst();
+ final Node f = first;
+ return (f == null) ? null : unlinkFirst(f);
}
/**
@@ -502,7 +696,7 @@ public class LinkedList
* Adds the specified element as the tail (last element) of this list.
*
* @param e the element to add
- * @return true (as specified by {@link Queue#offer})
+ * @return {@code true} (as specified by {@link Queue#offer})
* @since 1.5
*/
public boolean offer(E e) {
@@ -514,7 +708,7 @@ public class LinkedList
* Inserts the specified element at the front of this list.
*
* @param e the element to insert
- * @return true (as specified by {@link Deque#offerFirst})
+ * @return {@code true} (as specified by {@link Deque#offerFirst})
* @since 1.6
*/
public boolean offerFirst(E e) {
@@ -526,7 +720,7 @@ public class LinkedList
* Inserts the specified element at the end of this list.
*
* @param e the element to insert
- * @return true (as specified by {@link Deque#offerLast})
+ * @return {@code true} (as specified by {@link Deque#offerLast})
* @since 1.6
*/
public boolean offerLast(E e) {
@@ -536,58 +730,54 @@ public class LinkedList
/**
* Retrieves, but does not remove, the first element of this list,
- * or returns null if this list is empty.
+ * or returns {@code null} if this list is empty.
*
- * @return the first element of this list, or null
+ * @return the first element of this list, or {@code null}
* if this list is empty
* @since 1.6
*/
public E peekFirst() {
- if (size==0)
- return null;
- return getFirst();
- }
+ final Node f = first;
+ return (f == null) ? null : f.item;
+ }
/**
* Retrieves, but does not remove, the last element of this list,
- * or returns null if this list is empty.
+ * or returns {@code null} if this list is empty.
*
- * @return the last element of this list, or null
+ * @return the last element of this list, or {@code null}
* if this list is empty
* @since 1.6
*/
public E peekLast() {
- if (size==0)
- return null;
- return getLast();
+ final Node l = last;
+ return (l == null) ? null : l.item;
}
/**
* Retrieves and removes the first element of this list,
- * or returns null if this list is empty.
+ * or returns {@code null} if this list is empty.
*
- * @return the first element of this list, or null if
+ * @return the first element of this list, or {@code null} if
* this list is empty
* @since 1.6
*/
public E pollFirst() {
- if (size==0)
- return null;
- return removeFirst();
+ final Node f = first;
+ return (f == null) ? null : unlinkFirst(f);
}
/**
* Retrieves and removes the last element of this list,
- * or returns null if this list is empty.
+ * or returns {@code null} if this list is empty.
*
- * @return the last element of this list, or null if
+ * @return the last element of this list, or {@code null} if
* this list is empty
* @since 1.6
*/
public E pollLast() {
- if (size==0)
- return null;
- return removeLast();
+ final Node l = last;
+ return (l == null) ? null : unlinkLast(l);
}
/**
@@ -624,7 +814,7 @@ public class LinkedList
* does not contain the element, it is unchanged.
*
* @param o element to be removed from this list, if present
- * @return true if the list contained the specified element
+ * @return {@code true} if the list contained the specified element
* @since 1.6
*/
public boolean removeFirstOccurrence(Object o) {
@@ -637,21 +827,21 @@ public class LinkedList
* does not contain the element, it is unchanged.
*
* @param o element to be removed from this list, if present
- * @return true if the list contained the specified element
+ * @return {@code true} if the list contained the specified element
* @since 1.6
*/
public boolean removeLastOccurrence(Object o) {
- if (o==null) {
- for (Entry e = header.previous; e != header; e = e.previous) {
- if (e.element==null) {
- remove(e);
+ if (o == null) {
+ for (Node x = last; x != null; x = x.prev) {
+ if (x.item == null) {
+ unlink(x);
return true;
}
}
} else {
- for (Entry e = header.previous; e != header; e = e.previous) {
- if (o.equals(e.element)) {
- remove(e);
+ for (Node x = last; x != null; x = x.prev) {
+ if (o.equals(x.item)) {
+ unlink(x);
return true;
}
}
@@ -662,76 +852,68 @@ public class LinkedList
/**
* Returns a list-iterator of the elements in this list (in proper
* sequence), starting at the specified position in the list.
- * Obeys the general contract of List.listIterator(int).
+ * Obeys the general contract of {@code List.listIterator(int)}.
*
* The list-iterator is fail-fast: if the list is structurally
* modified at any time after the Iterator is created, in any way except
- * through the list-iterator's own remove or add
+ * through the list-iterator's own {@code remove} or {@code add}
* methods, the list-iterator will throw a
- * ConcurrentModificationException. Thus, in the face of
+ * {@code ConcurrentModificationException}. Thus, in the face of
* concurrent modification, the iterator fails quickly and cleanly, rather
* than risking arbitrary, non-deterministic behavior at an undetermined
* time in the future.
*
* @param index index of the first element to be returned from the
- * list-iterator (by a call to next)
+ * list-iterator (by a call to {@code next})
* @return a ListIterator of the elements in this list (in proper
* sequence), starting at the specified position in the list
* @throws IndexOutOfBoundsException {@inheritDoc}
* @see List#listIterator(int)
*/
public ListIterator listIterator(int index) {
+ checkPositionIndex(index);
return new ListItr(index);
}
private class ListItr implements ListIterator {
- private Entry lastReturned = header;
- private Entry next;
+ private Node lastReturned = null;
+ private Node next;
private int nextIndex;
private int expectedModCount = modCount;
ListItr(int index) {
- if (index < 0 || index > size)
- throw new IndexOutOfBoundsException("Index: "+index+
- ", Size: "+size);
- if (index < (size >> 1)) {
- next = header.next;
- for (nextIndex=0; nextIndexindex; nextIndex--)
- next = next.previous;
- }
+ // assert isPositionIndex(index);
+ next = (index == size) ? null : node(index);
+ nextIndex = index;
}
public boolean hasNext() {
- return nextIndex != size;
+ return nextIndex < size;
}
public E next() {
checkForComodification();
- if (nextIndex == size)
+ if (!hasNext())
throw new NoSuchElementException();
lastReturned = next;
next = next.next;
nextIndex++;
- return lastReturned.element;
+ return lastReturned.item;
}
public boolean hasPrevious() {
- return nextIndex != 0;
+ return nextIndex > 0;
}
public E previous() {
- if (nextIndex == 0)
+ checkForComodification();
+ if (!hasPrevious())
throw new NoSuchElementException();
- lastReturned = next = next.previous;
+ lastReturned = next = (next == null) ? last : next.prev;
nextIndex--;
- checkForComodification();
- return lastReturned.element;
+ return lastReturned.item;
}
public int nextIndex() {
@@ -739,36 +921,38 @@ public class LinkedList
}
public int previousIndex() {
- return nextIndex-1;
+ return nextIndex - 1;
}
public void remove() {
checkForComodification();
- Entry lastNext = lastReturned.next;
- try {
- LinkedList.this.remove(lastReturned);
- } catch (NoSuchElementException e) {
+ if (lastReturned == null)
throw new IllegalStateException();
- }
- if (next==lastReturned)
+
+ Node lastNext = lastReturned.next;
+ unlink(lastReturned);
+ if (next == lastReturned)
next = lastNext;
else
nextIndex--;
- lastReturned = header;
+ lastReturned = null;
expectedModCount++;
}
public void set(E e) {
- if (lastReturned == header)
+ if (lastReturned == null)
throw new IllegalStateException();
checkForComodification();
- lastReturned.element = e;
+ lastReturned.item = e;
}
public void add(E e) {
checkForComodification();
- lastReturned = header;
- addBefore(e, next);
+ lastReturned = null;
+ if (next == null)
+ linkLast(e);
+ else
+ linkBefore(e, next);
nextIndex++;
expectedModCount++;
}
@@ -779,41 +963,18 @@ public class LinkedList
}
}
- private static class Entry {
- E element;
- Entry next;
- Entry previous;
+ private static class Node {
+ E item;
+ Node next;
+ Node prev;
- Entry(E element, Entry next, Entry previous) {
- this.element = element;
+ Node(Node prev, E element, Node next) {
+ this.item = element;
this.next = next;
- this.previous = previous;
+ this.prev = prev;
}
}
- private Entry addBefore(E e, Entry entry) {
- Entry newEntry = new Entry(e, entry, entry.previous);
- newEntry.previous.next = newEntry;
- newEntry.next.previous = newEntry;
- size++;
- modCount++;
- return newEntry;
- }
-
- private E remove(Entry e) {
- if (e == header)
- throw new NoSuchElementException();
-
- E result = e.element;
- e.previous.next = e.next;
- e.next.previous = e.previous;
- e.next = e.previous = null;
- e.element = null;
- size--;
- modCount++;
- return result;
- }
-
/**
* @since 1.6
*/
@@ -821,9 +982,11 @@ public class LinkedList
return new DescendingIterator();
}
- /** Adapter to provide descending iterators via ListItr.previous */
- private class DescendingIterator implements Iterator {
- final ListItr itr = new ListItr(size());
+ /**
+ * Adapter to provide descending iterators via ListItr.previous
+ */
+ private class DescendingIterator implements Iterator {
+ private final ListItr itr = new ListItr(size());
public boolean hasNext() {
return itr.hasPrevious();
}
@@ -835,29 +998,32 @@ public class LinkedList
}
}
+ @SuppressWarnings("unchecked")
+ private LinkedList superClone() {
+ try {
+ return (LinkedList) super.clone();
+ } catch (CloneNotSupportedException e) {
+ throw new InternalError();
+ }
+ }
+
/**
- * Returns a shallow copy of this LinkedList. (The elements
+ * Returns a shallow copy of this {@code LinkedList}. (The elements
* themselves are not cloned.)
*
- * @return a shallow copy of this LinkedList instance
+ * @return a shallow copy of this {@code LinkedList} instance
*/
public Object clone() {
- LinkedList clone = null;
- try {
- clone = (LinkedList) super.clone();
- } catch (CloneNotSupportedException e) {
- throw new InternalError();
- }
+ LinkedList clone = superClone();
// Put clone into "virgin" state
- clone.header = new Entry(null, null, null);
- clone.header.next = clone.header.previous = clone.header;
+ clone.first = clone.last = null;
clone.size = 0;
clone.modCount = 0;
// Initialize clone with our elements
- for (Entry e = header.next; e != header; e = e.next)
- clone.add(e.element);
+ for (Node x = first; x != null; x = x.next)
+ clone.add(x.item);
return clone;
}
@@ -879,8 +1045,8 @@ public class LinkedList
public Object[] toArray() {
Object[] result = new Object[size];
int i = 0;
- for (Entry e = header.next; e != header; e = e.next)
- result[i++] = e.element;
+ for (Node x = first; x != null; x = x.next)
+ result[i++] = x.item;
return result;
}
@@ -894,7 +1060,7 @@ public class LinkedList
*
* If the list fits in the specified array with room to spare (i.e.,
* the array has more elements than the list), the element in the array
- * immediately following the end of the list is set to null.
+ * immediately following the end of the list is set to {@code null}.
* (This is useful in determining the length of the list only if
* the caller knows that the list does not contain any null elements.)
*
@@ -903,15 +1069,15 @@ public class LinkedList
* precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs.
*
- * Suppose x is a list known to contain only strings.
+ *
Suppose {@code x} is a list known to contain only strings.
* The following code can be used to dump the list into a newly
- * allocated array of String:
+ * allocated array of {@code String}:
*
*
* String[] y = x.toArray(new String[0]);
*
- * Note that toArray(new Object[0]) is identical in function to
- * toArray().
+ * Note that {@code toArray(new Object[0])} is identical in function to
+ * {@code toArray()}.
*
* @param a the array into which the elements of the list are to
* be stored, if it is big enough; otherwise, a new array of the
@@ -922,14 +1088,15 @@ public class LinkedList
* this list
* @throws NullPointerException if the specified array is null
*/
+ @SuppressWarnings("unchecked")
public 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 (Entry e = header.next; e != header; e = e.next)
- result[i++] = e.element;
+ for (Node x = first; x != null; x = x.next)
+ result[i++] = x.item;
if (a.length > size)
a[size] = null;
@@ -940,8 +1107,8 @@ public class LinkedList
private static final long serialVersionUID = 876323262645176354L;
/**
- * Save the state of this LinkedList instance to a stream (that
- * is, serialize it).
+ * Saves the state of this {@code LinkedList} instance to a stream
+ * (that is, serializes it).
*
* @serialData The size of the list (the number of elements it
* contains) is emitted (int), followed by all of its
@@ -956,14 +1123,15 @@ public class LinkedList
s.writeInt(size);
// Write out all elements in the proper order.
- for (Entry e = header.next; e != header; e = e.next)
- s.writeObject(e.element);
+ for (Node x = first; x != null; x = x.next)
+ s.writeObject(x.item);
}
/**
- * Reconstitute this LinkedList instance from a stream (that is
- * deserialize it).
+ * 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
@@ -972,12 +1140,8 @@ public class LinkedList
// Read in size
int size = s.readInt();
- // Initialize header
- header = new Entry(null, null, null);
- header.next = header.previous = header;
-
// Read in all elements in the proper order.
- for (int i=0; i q) {
q.clear();
- for (int i = 0; i < 5; i++)
+ for (int i = 0; i < 5; i++) {
+ testQueueAddRemove(q, null);
+ testQueueAddRemove(q, 537);
q.add(i);
+ }
equal(q.size(), 5);
checkFunctionalInvariants(q);
q.poll();
@@ -435,6 +438,216 @@ public class MOAT {
}
}
+ private static void testQueueAddRemove(final Queue q,
+ final Integer e) {
+ final List originalContents = new ArrayList(q);
+ final boolean isEmpty = q.isEmpty();
+ final boolean isList = (q instanceof List);
+ final List asList = isList ? (List) q : null;
+ check(!q.contains(e));
+ try {
+ q.add(e);
+ } catch (NullPointerException npe) {
+ check(e == null);
+ return; // Null elements not supported
+ }
+ check(q.contains(e));
+ check(q.remove(e));
+ check(!q.contains(e));
+ equal(new ArrayList(q), originalContents);
+
+ if (q instanceof Deque>) {
+ final Deque deq = (Deque) q;
+ final List singleton = Collections.singletonList(e);
+
+ // insert, query, remove element at head
+ if (isEmpty) {
+ THROWS(NoSuchElementException.class,
+ new Fun(){void f(){ deq.getFirst(); }},
+ new Fun(){void f(){ deq.element(); }},
+ new Fun(){void f(){ deq.iterator().next(); }});
+ check(deq.peekFirst() == null);
+ check(deq.peek() == null);
+ } else {
+ check(deq.getFirst() != e);
+ check(deq.element() != e);
+ check(deq.iterator().next() != e);
+ check(deq.peekFirst() != e);
+ check(deq.peek() != e);
+ }
+ check(!deq.contains(e));
+ check(!deq.removeFirstOccurrence(e));
+ check(!deq.removeLastOccurrence(e));
+ if (isList) {
+ check(asList.indexOf(e) == -1);
+ check(asList.lastIndexOf(e) == -1);
+ }
+ switch (rnd.nextInt(isList ? 4 : 3)) {
+ case 0: deq.addFirst(e); break;
+ case 1: check(deq.offerFirst(e)); break;
+ case 2: deq.push(e); break;
+ case 3: asList.add(0, e); break;
+ default: throw new AssertionError();
+ }
+ check(deq.peekFirst() == e);
+ check(deq.getFirst() == e);
+ check(deq.element() == e);
+ check(deq.peek() == e);
+ check(deq.iterator().next() == e);
+ check(deq.contains(e));
+ if (isList) {
+ check(asList.get(0) == e);
+ check(asList.indexOf(e) == 0);
+ check(asList.lastIndexOf(e) == 0);
+ check(asList.subList(0, 1).equals(singleton));
+ }
+ switch (rnd.nextInt(isList ? 11 : 9)) {
+ case 0: check(deq.pollFirst() == e); break;
+ case 1: check(deq.removeFirst() == e); break;
+ case 2: check(deq.remove() == e); break;
+ case 3: check(deq.pop() == e); break;
+ case 4: check(deq.removeFirstOccurrence(e)); break;
+ case 5: check(deq.removeLastOccurrence(e)); break;
+ case 6: check(deq.remove(e)); break;
+ case 7: check(deq.removeAll(singleton)); break;
+ case 8: Iterator it = deq.iterator(); it.next(); it.remove(); break;
+ case 9: asList.remove(0); break;
+ case 10: asList.subList(0, 1).clear(); break;
+ default: throw new AssertionError();
+ }
+ if (isEmpty) {
+ THROWS(NoSuchElementException.class,
+ new Fun(){void f(){ deq.getFirst(); }},
+ new Fun(){void f(){ deq.element(); }},
+ new Fun(){void f(){ deq.iterator().next(); }});
+ check(deq.peekFirst() == null);
+ check(deq.peek() == null);
+ } else {
+ check(deq.getFirst() != e);
+ check(deq.element() != e);
+ check(deq.iterator().next() != e);
+ check(deq.peekFirst() != e);
+ check(deq.peek() != e);
+ }
+ check(!deq.contains(e));
+ check(!deq.removeFirstOccurrence(e));
+ check(!deq.removeLastOccurrence(e));
+ if (isList) {
+ check(isEmpty || asList.get(0) != e);
+ check(asList.indexOf(e) == -1);
+ check(asList.lastIndexOf(e) == -1);
+ }
+ equal(new ArrayList(deq), originalContents);
+
+ // insert, query, remove element at tail
+ if (isEmpty) {
+ check(deq.peekLast() == null);
+ THROWS(NoSuchElementException.class,
+ new Fun(){void f(){ deq.getLast(); }});
+ } else {
+ check(deq.peekLast() != e);
+ check(deq.getLast() != e);
+ }
+ switch (rnd.nextInt(isList ? 6 : 4)) {
+ case 0: deq.addLast(e); break;
+ case 1: check(deq.offerLast(e)); break;
+ case 2: check(deq.add(e)); break;
+ case 3: deq.addAll(singleton); break;
+ case 4: asList.addAll(deq.size(), singleton); break;
+ case 5: asList.add(deq.size(), e); break;
+ default: throw new AssertionError();
+ }
+ check(deq.peekLast() == e);
+ check(deq.getLast() == e);
+ check(deq.contains(e));
+ if (isList) {
+ ListIterator it = asList.listIterator(asList.size());
+ check(it.previous() == e);
+ check(asList.get(asList.size() - 1) == e);
+ check(asList.indexOf(e) == asList.size() - 1);
+ check(asList.lastIndexOf(e) == asList.size() - 1);
+ int size = asList.size();
+ check(asList.subList(size - 1, size).equals(singleton));
+ }
+ switch (rnd.nextInt(isList ? 8 : 6)) {
+ case 0: check(deq.pollLast() == e); break;
+ case 1: check(deq.removeLast() == e); break;
+ case 2: check(deq.removeFirstOccurrence(e)); break;
+ case 3: check(deq.removeLastOccurrence(e)); break;
+ case 4: check(deq.remove(e)); break;
+ case 5: check(deq.removeAll(singleton)); break;
+ case 6: asList.remove(asList.size() - 1); break;
+ case 7:
+ ListIterator it = asList.listIterator(asList.size());
+ it.previous();
+ it.remove();
+ break;
+ default: throw new AssertionError();
+ }
+ if (isEmpty) {
+ check(deq.peekLast() == null);
+ THROWS(NoSuchElementException.class,
+ new Fun(){void f(){ deq.getLast(); }});
+ } else {
+ check(deq.peekLast() != e);
+ check(deq.getLast() != e);
+ }
+ check(!deq.contains(e));
+ equal(new ArrayList(deq), originalContents);
+
+ // Test operations on empty deque
+ switch (rnd.nextInt(isList ? 4 : 2)) {
+ case 0: deq.clear(); break;
+ case 1:
+ Iterator it = deq.iterator();
+ while (it.hasNext()) {
+ it.next();
+ it.remove();
+ }
+ break;
+ case 2: asList.subList(0, asList.size()).clear(); break;
+ case 3:
+ ListIterator lit = asList.listIterator(asList.size());
+ while (lit.hasPrevious()) {
+ lit.previous();
+ lit.remove();
+ }
+ break;
+ default: throw new AssertionError();
+ }
+ testEmptyCollection(deq);
+ check(!deq.iterator().hasNext());
+ if (isList) {
+ check(!asList.listIterator().hasPrevious());
+ THROWS(NoSuchElementException.class,
+ new Fun(){void f(){ asList.listIterator().previous(); }});
+ }
+ THROWS(NoSuchElementException.class,
+ new Fun(){void f(){ deq.iterator().next(); }},
+ new Fun(){void f(){ deq.element(); }},
+ new Fun(){void f(){ deq.getFirst(); }},
+ new Fun(){void f(){ deq.getLast(); }},
+ new Fun(){void f(){ deq.pop(); }},
+ new Fun(){void f(){ deq.remove(); }},
+ new Fun(){void f(){ deq.removeFirst(); }},
+ new Fun(){void f(){ deq.removeLast(); }});
+
+ check(deq.poll() == null);
+ check(deq.pollFirst() == null);
+ check(deq.pollLast() == null);
+ check(deq.peek() == null);
+ check(deq.peekFirst() == null);
+ check(deq.peekLast() == null);
+ check(!deq.removeFirstOccurrence(e));
+ check(!deq.removeLastOccurrence(e));
+
+ check(deq.addAll(originalContents) == !isEmpty);
+ equal(new ArrayList(deq), originalContents);
+ check(!deq.addAll(Collections.emptyList()));
+ equal(new ArrayList(deq), originalContents);
+ }
+ }
+
private static void testQueueIteratorRemove(Queue q) {
System.err.printf("testQueueIteratorRemove %s%n",
q.getClass().getSimpleName());