深入浅析Java中的链表

public class LinkedList {    private class Data{      private Object obj;      private Data next = null;            Data(Object obj){        this.obj = obj;      }    }    private Data first = null;        public void insertFirst(Object obj){      Data data = new Data(obj);      data.next = first;      first = data;    }    public Object deleteFirst() throws Exception{      if(first == null)        throw new Exception("empty!");      Data temp = first;      first = first.next;      return temp.obj;    }        public Object find(Object obj) throws Exception{      if(first == null)        throw new Exception("LinkedList is empty!");      Data cur = first;      while(cur != null){        if(cur.obj.equals(obj)){          return cur.obj;        }        cur = cur.next;      }      return null;    }    public void remove(Object obj) throws Exception{      if(first == null)        throw new Exception("LinkedList is empty!");      if(first.obj.equals(obj)){        first = first.next;      }else{        Data pre = first;        Data cur = first.next;        while(cur != null){          if(cur.obj.equals(obj)){            pre.next = cur.next;          }         pre = cur;          cur = cur.next;        }      }    }    public boolean isEmpty(){      return (first == null);    }    public void display(){      if(first == null)        System.out.println("empty");      Data cur = first;      while(cur != null){        System.out.print(cur.obj.toString() + " -> ");        cur = cur.next;      }      System.out.print("\n");    }        public static void main(String[] args) throws Exception {      LinkedList ll = new LinkedList();      ll.insertFirst(4);      ll.insertFirst(3);      ll.insertFirst(2);      ll.insertFirst(1);      ll.display();      ll.deleteFirst();      ll.display();      ll.remove(3);      ll.display();      System.out.println(ll.find(1));      System.out.println(ll.find(4));    }  }