数据结构学习（五） Java链表实现队列

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package queue;   /**  * @Title: LinkedListQueue  * @ProjectName demo  */ public class LinkedListQueue<E> implements Queue<E> {       private class Node {         private Node next;         private E e;           public Node(E e, Node next) {             this.next = next;             this.e = e;         }           public Node(E e) {             this(e, null);         }           @Override         public String toString() {             return e.toString();         }     }       private int size;     private Node head, tail;       public LinkedListQueue() {         size = 0;         head = null;         tail = null;     }       @Override     public int getSize() {         return size;     }       @Override     public boolean isEmpty() {         return size == 0;     }       @Override     public void enqueue(E e) {         if (tail == null) {             tail = new Node(e);             head = tail;         }else{             tail.next = new Node(e);             tail = tail.next;         }         size ++;     }       @Override     public E dequeue() {         if (isEmpty()){             throw new IllegalArgumentException("dequeue error..");         }         Node cur = head;         head = head.next;         cur.next = null;         if (head == null){             tail = null;         }         size--;         return cur.e;     }       @Override     public E getFront() {         if (isEmpty()){             throw new IllegalArgumentException("GetFront error..");         }         return head.e;     }       @Override     public String toString() {         StringBuilder sb = new StringBuilder("front:");         Node h = head;         while (h != null) {             sb.append("--->"+h.e);             h = h.next;         }         sb.append("tail");         return sb.toString();     } }