103-104_容器_JDK源代码分析_自己实现LinkedList

public class MyLinkedList/*implements List*/{    class Node{        Node previous;        Object obj;        Node next;    }    private Node first;    private Node last;    private int size;    public int size(){        return size;    }       //索引越界检测    private void rangeCheck(int index){        if(index<0||index>=size){            try {                throw new Exception();            } catch (Exception e) {                e.printStackTrace();            }        }    }    //根据索引找到相关节点    public Node node(int index){        Node temp = null;        if(first!=null){            if (index < (size >> 1)) {                temp = first;                for(int i=0;i<index;i++){                    temp = temp.next;                }            }else{                temp = last;                for (int i = size - 1; i > index; i--){                    temp = temp.previous;                }            }           }        return temp;    }    public void add(Object obj){        Node n = new Node();        if(first==null){            n.previous=null;            n.obj=obj;            n.next=null;            first = n;            last = n;        }else{            //直接往last节点后增加新的节点            n.previous=last;            n.obj=obj;            n.next=null;            last.next=n;            last = n;        }            size++;    }    public Object get(int index){   //2        rangeCheck(index);        // 0 1 2 3 4        Node temp = node(index);        if(temp!=null){            return temp.obj;        }        return null;    }    public void remove(int index){        Node temp = node(index);        if(temp!=null){            Node up = temp.previous;            Node down = temp.next;            up.next = down;            down.previous = up;            size--;        }    }    public void add(int index,Object obj){        Node temp = node(index);        Node newNode = new Node();        newNode.obj = obj;        if(temp!=null){            Node up = temp.previous;            up.next = newNode;            newNode.previous = up;            newNode.next = temp;            temp.previous = newNode;            size++;        }    }    public static void main(String[] args) {        MyLinkedList list = new MyLinkedList();        list.add("aaa");        list.add("bbb");//      list.add(1,"BBBB");        list.add("ccc");        list.add("ddd");        list.add("eee");//      list.remove(1);        System.out.println(list.get(3));     }       }