java - 为什么我的单链表实现在添加对象后两次给出我的第一个元素？

Question

这里我尝试实现“单链表”的基本操作。但只有在这里我只面临一个问题，即添加元素后，即

al.add("Ravi");
al.add("Vijay");
al.add("Sanjay");
al.add("Ajay"); 

我得到的输出为:
[]--------->对于空链表
[Ravi,Ravi,Vijay,Sanjay,Ajay]------>添加元素后。

class MyLinkedList {
        private Node first;
        private Node last;
        private int count;

        public void add(Object ele){
            if(first==null){
                first=new Node(ele);
                last=first;
                count++;
            }
            last.next=new Node(ele);
            last=last.next;
            count++;
        }
        public int size(){
            return count;
        }
        public Object get(int index){
            if(index>=size())throw new IndexOutOfBoundsException();
            Node p=first;
            for(int i=0;i<=index;i++){
                p=p.next;
            }
            return p.ele;
        }
        public void remove(int index){
            if(index>=size())throw new IndexOutOfBoundsException();
            if(index==0){
                first=first.next;
                count--;
                return;
            }
        }

        @Override
        public String toString() {
            if(size()==0)return "[]";
            Node p=first;
            String s="[" + p.ele;
            while(p.next!=null){
                p=p.next;
                s+=","+p.ele;
            }
            return s + "]";
        }

        private class Node{
            Object ele;
            Node next;
            Node(Object ele){
                this.ele=ele;
            }
        }

        public static void main(String[] args) {
             MyLinkedList al=new MyLinkedList(); 
             System.out.println(al);
              al.add("Ravi");  
              al.add("Vijay");  
              al.add("Sanjay");  
              al.add("Ajay");
              System.out.println(al);

        }

    }

Answer 1

因为你添加了两次:

    public void **add**(Object ele){
        if(first==null){
            first=new Node(ele); //First
            last=first;
            count++;
        }
        last.next=new Node(ele); //second.
        last=last.next;
        count++;
    }

添加 else 语句:

    public void **add**(Object ele){
        if(first==null){
            first=new Node(ele);
            last=first;
            count++;
        } else {
          last.next=new Node(ele);
          last=last.next;
          count++;
        }
    }