【java】【java Collection】LinkedList
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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 msiteratorLinkedListThruForeach：3759 msiteratorThroughFor2：4 msiteratorThroughPollFirst：3 msiteratorThroughPollLast：3 msiteratorThroughRemoveFirst：3 msiteratorThroughRemoveLast：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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