【java】【java Collection】LinkedList，
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【java】【java Collection】LinkedList，
源代码;
package java.util;
import java.util.function.Consumer;
/**
* Doubly-linked list implementation of the List and Deque interfaces. (实现队列和双端队列)
* Implements all optional list operations, and permits all elements (including null).
*
* 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.
*
* Note that this implementation is not synchronized.(非同步)
* If multiple threads access a linked list concurrently, and at least one of the threads modifies the list structurally, it must be synchronized externally.
*(A structural modification is any operation that adds or deletes one or more elements; merely setting the value of an element is not a structural modification.)
*This is typically accomplished by synchronizing on some object that naturally encapsulates the list.
*
* If no such object exists, the list should be "wrapped" using the
* {@link Collections#synchronizedList Collections.synchronizedList}
* method. This is best done at creation time, to prevent accidental
* unsynchronized access to the list:<pre>
* List list = Collections.synchronizedList(new LinkedList(...));</pre>
*
* <p>The iterators returned by this class's {@code iterator} and
* {@code listIterator} methods are <i>fail-fast</i>: if the list is
* structurally modified at any time after the iterator is created, in
* 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
* time in the future.
*
* <p>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 {@code ConcurrentModificationException} on a best-effort basis.
* Therefore, it would be wrong to write a program that depended on this
* exception for its correctness: <i>the fail-fast behavior of iterators
* should be used only to detect bugs.</i>
*
*/
/*
序列化补充：
父类实现序列化 子类都是能够被序列化;如果父类没有实现序列化，子类实现Serializable接口，子类也是能够序列化的
static和transient两类对象无法实现序列化
*/
public class LinkedList<E>
extends AbstractSequentialList<E>
implements List<E>, Deque<E>, Cloneable, java.io.Serializable
{
//LinkedList中元素个数
transient int size = 0;
//内部节点类
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;
}
}
//找到如何设置头结点和尾节点的代码
/**
* Pointer to first node.
* Invariant: (first == null && last == null) ||
* (first.prev == null && first.item != null)
*/
transient Node<E> first;
/**
* Pointer to last node.
* Invariant: (first == null && last == null) ||
* (last.next == null && last.item != null)
*/
transient Node<E> last;
public LinkedList() {
}
public LinkedList(Collection<? extends E> c) {
this();//调用上面的无参构造函数
addAll(c);
}
private boolean isPositionIndex(int index) {
return index >= 0 && index <= size;
}
private String outOfBoundsMsg(int index) {
return "Index: "+index+", Size: "+size;
}
private void checkPositionIndex(int index) {
if (!isPositionIndex(index))
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
private boolean isElementIndex(int index) {
return index >= 0 && index < size;
}
//获取索引在index的节点
Node<E> node(int index) {
//assert isElementIndex(index);
//节点在前半段
if (index < (size >> 1)) {
Node<E> x = first;
for (int i = 0; i < index; i++)
x = x.next;
return x;
} else {
//节点在后半段
Node<E> x = last;
for (int i = size - 1; i > index; i--)
x = x.prev;
return x;
}
}
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; //如果没有元素需要添加 就直接返回false
Node<E> pred, succ;//succ表示index对应位置的元素 pred代表其前一个元素
if (index == size) {//插入的位置是最后一个元素下一位
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)//pred如果为null 说明原本的链表就为空
first = newNode;//则将新生成的节点作为first节点
else
pred.next = newNode;//否则将刚生成的节点作为pred的后继节点
pred = newNode;//循环插入节点
}
//如果succ为空 代表是在双向链表的末尾开始插入元素 那么其新插入的最后一个节点要设置成last节点
if (succ == null) {
last = pred;
} else {
//否则要将index节点和新插入的节点之间构成双向箭头
pred.next = succ;
succ.prev = pred;
}
size += numNew;//元素个数增加
modCount++;//迭代器修改次数
return true;
}
//将节点设置成first节点
private void linkFirst(E e) {
final Node<E> f = first;
final Node<E> newNode = new Node<>(null, e, f);
first = newNode;
if (f == null)//如果原本LinkedList为空 那么last和first都是指向同一个位置的
last = newNode;
else
f.prev = newNode;//将原来的first节点前引用指向newnode 后引用在new Node<>(null, e, f)就已经设置好了 所以就不需要写了
size++;
modCount++;
}
//将节点设置成为尾节点
void linkLast(E e) {
final Node<E> l = last;
final Node<E> newNode = new Node<>(l, e, null);
last = newNode;
if (l == null)//如果原LinkedList为空 则first和last都是需要指向newNode
first = newNode;
else
l.next = newNode;//双向操作
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;//顺序不要弄反 这里因为已经将succ.prev给了pred 所以顺序反了也是不会影响最后的效果的
if (pred == null)
first = newNode;//头结点之前插入节点
else
pred.next = newNode;
size++;
modCount++;
}
//去掉第一个节点 返回其节点值
private E unlinkFirst(Node<E> f) {
// assert f == first && f != null; //指定节点必须为first且first必须不为空
final E element = f.item;
final Node<E> next = f.next;
f.item = null;
f.next = null; // help GC
first = next;
if (next == null)//如果原本只有一个节点 那么last也就是需要设置成空
last = null;
else
next.prev = null;//否则原本first.next指向first引用
size--;//元素个数减一
modCount++;
return element;
}
//去掉尾节点
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;//如果LinkedList原本就只有一个节点 则其首节点也必须设置为空
else
prev.next = null;
size--;
modCount++;
return element;
}
//去除指定节点
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;
//下面代码会产生四种组合
//头节点
//1.prev和next都为null 孤立的一个节点 first = next; last = prev; 此时first和last都会null
//2.prev == null&&next！=null 设置头结点 加上去除原头结点和其下一个节点之间的关系
//尾节点
//3.prev ！= null &&next==null
//中间节点
if (prev == null) { //如果要删除的节点是first节点
first = next;
} else {
prev.next = next;
x.prev = null;//help gc
}
if (next == null) { //如果要删除的节点是last节点
last = prev;
} else {
next.prev = prev;
x.next = null;//help gc
}
x.item = null;//help gc
size--;
modCount++;
return element;
}
//返回首节点的元素值
public E getFirst() {
final Node<E> f = first;
if (f == null)
throw new NoSuchElementException();
return f.item;
}
//返回尾节点的元素值
public E getLast() {
final Node<E> l = last;
if (l == null)
throw new NoSuchElementException();
return l.item;
}
//移除首节点
public E removeFirst() {
final Node<E> f = first;
if (f == null)
throw new NoSuchElementException();
return unlinkFirst(f);
}
//移除尾节点
public E removeLast() {
final Node<E> l = last;
if (l == null)
throw new NoSuchElementException();
return unlinkLast(l);
}
//在first节点之前插入节点
public void addFirst(E e) {
linkFirst(e);
}
//在last插入节点
public void addLast(E e) {
linkLast(e);
}
//对象o需要判断是否为null
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 boolean contains(Object o) {
return indexOf(o) != -1;
}
// Returns the number of elements in this list.
public int size() {
return size;
}
//在LinkedList末尾插入元素
public boolean add(E e) {
linkLast(e);
return true;
}
//去除指定节点 第一次出现节点
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;
}
//清空LinkedList
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++;
}
private void checkElementIndex(int index) {
if (!isElementIndex(index))
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
//返回节点值
public E get(int index) {
checkElementIndex(index);//确保下标在范围内
return node(index).item;
}
//设置节点的值
public E set(int index, E element) {
checkElementIndex(index);
Node<E> x = node(index);
E oldVal = x.item;
x.item = element;
return oldVal;
}
//插入节点 如果插入的位置是last后面一个位置 否则就是在index节点之前插入元素
public void add(int index, E element) {
checkPositionIndex(index);
if (index == size)
linkLast(element);
else
linkBefore(element, node(index));
}
//移除节点
public E remove(int index) {
checkElementIndex(index);
return unlink(node(index));
}
//分节点为null和不为null两种情况
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;
}
// Queue operations.
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);
}
// Deque operations
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);
}
//从后往前遍历 删除第一次出现的节点值
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();
}
}
/**
* @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();
}
}
/*
Object中的clone()
protected native Object clone() throws CloneNotSupportedException;
本地方法
*/
@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;
}
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;
//Saves the state of this LinkedList instance to a stream
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 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());
}
/**
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
* and <em>fail-fast</em> {@link Spliterator} over the elements in this
* list.
*
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED} and
* {@link Spliterator#ORDERED}. Overriding implementations should document
* the reporting of additional characteristic values.
*
* @implNote
* The {@code Spliterator} additionally reports {@link Spliterator#SUBSIZED}
* and implements {@code trySplit} to permit limited parallelism..
*
* @return a {@code Spliterator} over the elements in this list
* @since 1.8
*/
@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;
}
}
}
package Test.fast;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.NoSuchElementException;
public class LinkedListThruTest {
public static void main(String[] args) {
// 通过Iterator遍历LinkedList
iteratorLinkedListThruIterator(getLinkedList()) ;
// 通过快速随机访问遍历LinkedList
iteratorLinkedListThruForeach(getLinkedList()) ;
// 通过for循环的变种来访问遍历LinkedList
iteratorThroughFor2(getLinkedList()) ;
// 通过PollFirst()遍历LinkedList
iteratorThroughPollFirst(getLinkedList()) ;
// 通过PollLast()遍历LinkedList
iteratorThroughPollLast(getLinkedList()) ;
// 通过removeFirst()遍历LinkedList
iteratorThroughRemoveFirst(getLinkedList()) ;
// 通过removeLast()遍历LinkedList
iteratorThroughRemoveLast(getLinkedList()) ;
}
private static LinkedList getLinkedList() {
LinkedList llist = new LinkedList();
for (int i=0; i<100000; i++)
llist.addLast(i);
return llist;
}
/**
* 通过快迭代器遍历LinkedList
*/
private static void iteratorLinkedListThruIterator(LinkedList<Integer> list) {
if (list == null)
return ;
// 记录开始时间
long start = System.currentTimeMillis();
for(Iterator iter = list.iterator(); iter.hasNext();)
iter.next();
// 记录结束时间
long end = System.currentTimeMillis();
long interval = end - start;
System.out.println("iteratorLinkedListThruIterator：" + interval+" ms");
}
/**
* 通过快速随机访问遍历LinkedList
*/
private static void iteratorLinkedListThruForeach(LinkedList<Integer> list) {
if (list == null)
return ;
// 记录开始时间
long start = System.currentTimeMillis();
int size = list.size();
for (int i=0; i<size; i++) {
list.get(i);
}
// 记录结束时间
long end = System.currentTimeMillis();
long interval = end - start;
System.out.println("iteratorLinkedListThruForeach：" + interval+" ms");
}
/**
* 通过另外一种for循环来遍历LinkedList
*/
private static void iteratorThroughFor2(LinkedList<Integer> list) {
if (list == null)
return ;
// 记录开始时间
long start = System.currentTimeMillis();
for (Integer integ:list)
;
// 记录结束时间
long end = System.currentTimeMillis();
long interval = end - start;
System.out.println("iteratorThroughFor2：" + interval+" ms");
}
/**
* 通过pollFirst()来遍历LinkedList
*/
private static void iteratorThroughPollFirst(LinkedList<Integer> list) {
if (list == null)
return ;
// 记录开始时间
long start = System.currentTimeMillis();
while(list.pollFirst() != null)
;
// 记录结束时间
long end = System.currentTimeMillis();
long interval = end - start;
System.out.println("iteratorThroughPollFirst：" + interval+" ms");
}
/**
* 通过pollLast()来遍历LinkedList
*/
private static void iteratorThroughPollLast(LinkedList<Integer> list) {
if (list == null)
return ;
// 记录开始时间
long start = System.currentTimeMillis();
while(list.pollLast() != null)
;
// 记录结束时间
long end = System.currentTimeMillis();
long interval = end - start;
System.out.println("iteratorThroughPollLast：" + interval+" ms");
}
/**
* 通过removeFirst()来遍历LinkedList
*/
private static void iteratorThroughRemoveFirst(LinkedList<Integer> list) {
if (list == null)
return ;
// 记录开始时间
long start = System.currentTimeMillis();
try {
while(list.removeFirst() != null)
;
} catch (NoSuchElementException e) {
}
// 记录结束时间
long end = System.currentTimeMillis();
long interval = end - start;
System.out.println("iteratorThroughRemoveFirst：" + interval+" ms");
}
/**
* 通过removeLast()来遍历LinkedList
*/
private static void iteratorThroughRemoveLast(LinkedList<Integer> list) {
if (list == null)
return ;
// 记录开始时间
long start = System.currentTimeMillis();
try {
while(list.removeLast() != null)
;
} catch (NoSuchElementException e) {
}
// 记录结束时间
long end = System.currentTimeMillis();
long interval = end - start;
System.out.println("iteratorThroughRemoveLast：" + interval+" ms");
}
}iteratorLinkedListThruIterator：13 ms
iteratorLinkedListThruForeach：3759 ms
iteratorThroughFor2：4 ms
iteratorThroughPollFirst：3 ms
iteratorThroughPollLast：3 ms
iteratorThroughRemoveFirst：3 ms
iteratorThroughRemoveLast：4 ms随机访问是最慢的
示例代码：
package Test.fast;
import java.util.LinkedList;
public class LinkedListTest {
public static void main(String[] args) {
// 测试LinkedList的API
testLinkedListAPIs() ;
// 将LinkedList当作 LIFO(后进先出)的堆栈
useLinkedListAsLIFO();
// 将LinkedList当作 FIFO(先进先出)的队列
useLinkedListAsFIFO();
}
/*
* 测试LinkedList中部分API
*/
private static void testLinkedListAPIs() {
String val = null;
//LinkedList llist;
//llist.offer("10");
// 新建一个LinkedList
LinkedList llist = new LinkedList();
//---- 添加操作 ----
// 依次添加1,2,3
llist.add("1");
llist.add("2");
llist.add("3");
// 将“4”添加到第一个位置
llist.add(1, "4");
System.out.println("\nTest \"addFirst(), removeFirst(), getFirst()\"");
// (01) 将“10”添加到第一个位置。 失败的话，抛出异常！
llist.addFirst("10");
System.out.println("llist:"+llist);
// (02) 将第一个元素删除。 失败的话，抛出异常！
System.out.println("llist.removeFirst():"+llist.removeFirst());
System.out.println("llist:"+llist);
// (03) 获取第一个元素。 失败的话，抛出异常！
System.out.println("llist.getFirst():"+llist.getFirst());
System.out.println("\nTest \"offerFirst(), pollFirst(), peekFirst()\"");
// (01) 将“10”添加到第一个位置。 返回true。
llist.offerFirst("10");
System.out.println("llist:"+llist);
// (02) 将第一个元素删除。 失败的话，返回null。
System.out.println("llist.pollFirst():"+llist.pollFirst());
System.out.println("llist:"+llist);
// (03) 获取第一个元素。 失败的话，返回null。
System.out.println("llist.peekFirst():"+llist.peekFirst());
System.out.println("\nTest \"addLast(), removeLast(), getLast()\"");
// (01) 将“20”添加到最后一个位置。 失败的话，抛出异常！
llist.addLast("20");
System.out.println("llist:"+llist);
// (02) 将最后一个元素删除。 失败的话，抛出异常！
System.out.println("llist.removeLast():"+llist.removeLast());
System.out.println("llist:"+llist);
// (03) 获取最后一个元素。 失败的话，抛出异常！
System.out.println("llist.getLast():"+llist.getLast());
System.out.println("\nTest \"offerLast(), pollLast(), peekLast()\"");
// (01) 将“20”添加到第一个位置。 返回true。
llist.offerLast("20");
System.out.println("llist:"+llist);
// (02) 将第一个元素删除。 失败的话，返回null。
System.out.println("llist.pollLast():"+llist.pollLast());
System.out.println("llist:"+llist);
// (03) 获取第一个元素。 失败的话，返回null。
System.out.println("llist.peekLast():"+llist.peekLast());
// 将第3个元素设置300。不建议在LinkedList中使用此操作，因为效率低！
llist.set(2, "300");
// 获取第3个元素。不建议在LinkedList中使用此操作，因为效率低！
System.out.println("\nget(3):"+llist.get(2));
// ---- toArray(T[] a) ----
// 将LinkedList转行为数组
String[] arr = (String[])llist.toArray(new String[0]);
for (String str:arr)
System.out.println("str:"+str);
// 输出大小
System.out.println("size:"+llist.size());
// 清空LinkedList
llist.clear();
// 判断LinkedList是否为空
System.out.println("isEmpty():"+llist.isEmpty()+"\n");
}
/**
* 将LinkedList当作 LIFO(后进先出)的堆栈
*/
private static void useLinkedListAsLIFO() {
System.out.println("\nuseLinkedListAsLIFO");
// 新建一个LinkedList
LinkedList stack = new LinkedList();
// 将1,2,3,4添加到堆栈中
stack.push("1");
stack.push("2");
stack.push("3");
stack.push("4");
// 打印“栈”
System.out.println("stack:"+stack);
// 删除“栈顶元素”
System.out.println("stack.pop():"+stack.pop());
// 取出“栈顶元素”
System.out.println("stack.peek():"+stack.peek());
// 打印“栈”
System.out.println("stack:"+stack);
}
/**
* 将LinkedList当作 FIFO(先进先出)的队列
*/
private static void useLinkedListAsFIFO() {
System.out.println("\nuseLinkedListAsFIFO");
// 新建一个LinkedList
LinkedList queue = new LinkedList();
// 将10,20,30,40添加到队列。每次都是插入到末尾
queue.add("10");
queue.add("20");
queue.add("30");
queue.add("40");
// 打印“队列”
System.out.println("queue:"+queue);
// 删除(队列的第一个元素)
System.out.println("queue.remove():"+queue.remove());
// 读取(队列的第一个元素)
System.out.println("queue.element():"+queue.element());
// 打印“队列”
System.out.println("queue:"+queue);
}
}参考资料:
http://www.cnblogs.com/skywang12345/p/3308807.html
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