Java-链表实现.

什么是链表

链表 [Linked List]：链表是由一组不必相连不必相连：可以连续也可以不连续的内存结构 节点，按特定的顺序链接在一起的抽象数据类型。

补充：
抽象数据类型（Abstract Data Type [ADT]）：表示数学中抽象出来的一些操作的集合。
内存结构：内存中的结构，如：struct、特殊内存块…等等之类；

• 最简单的数据结构
• 更深入的理解引用，指针
• 更深入的理解递归
• 辅助组成其他数据结构

优缺点

• 优点：真正的动态，不需要处理固定容量的问题
• 缺点：丧失了随机访问的能力

代码实现

package dataStructure;

public class LinkedList<E> {

    private class Node {
        public E e;
        public Node next;

        public Node(E e, Node next) {
            this.e = e;
            this.next = next;
        }

        public Node(E e) {
            this(e, null);
        }

        public Node() {
            this(null, null);
        }

        public String toString() {
            return e.toString();
        }
    }

    private Node dummyHead;
    private int size;

    public LinkedList() {
        dummyHead = new Node();
        size = 0;
    }

    public int getSize() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    public void add(int index, E e) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("Add failed, Illegal index.");
        }

        Node pre = dummyHead;
        for (int i = 0; i < index; i++) {
            pre = pre.next;
        }

        /*
        Node node = new Node(e);
        node.next = pre.next;
        pre.next = node;
        */

        pre.next = new Node(e, pre.next);
        size++;
    }

    public void addFirst(E e) {
        add(0, e);
    }

    public void addLast(E e) {
        add(size, e);
    }

    public E get(int index) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("Get failed, Illegal index.");
        }
        Node curr = dummyHead.next;
        for (int i = 0; i < index; i++) {
            curr = curr.next;
        }
        return curr.e;
    }

    // 获得链表的第一个元素
    public E getFirst() {
        return get(0);
    }

    // 获得链表的最后一个元素
    public E getLast() {
        return get(size - 1);
    }

    public void set(int index, E e) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("Set failed, Illegal index.");
        }
        Node curr = dummyHead.next;
        /*
        while(curr != null){
            if (curr.e.equals(e)){
                curr.e = e;
                return;
            }
            curr = curr.next;
        }*/
        for (int i = 0; i < index; i++) {
            curr = curr.next;
        }
        curr.e = e;
    }

    public boolean contain(E e) {
        Node curr = dummyHead.next;
        while (curr != null) {
            if (curr.e.equals(e)) {
                return true;
            }
            curr = curr.next;
        }
        return false;
    }

    public E remove(int index) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("Delete failed, Illegal index.");
        }
        Node preNode = dummyHead;
        for (int i = 0; i < index; i++) {
            preNode = preNode.next;
        }
        Node delNode = preNode.next;
        preNode.next = delNode.next;
        delNode.next = null;
        size--;
        return delNode.e;
    }

    public E removeFirst() {
        return remove(0);
    }

    public E removeLast() {
        return remove(size - 1);
    }

    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();
        Node curr = dummyHead.next;
        while (curr != null) {
            res.append(curr + "->");
            curr = curr.next;
        }
        res.append("Null");
        return res.toString();
    }
    
}