Question

 public static int readConvert(char[]post)throws IOException{
    Stack S = new Stack();
    int j=0;
    char c;
    System.out.printf("Type an infix expression and press Enter\n");
    char token =getToken();
    while (token!='\0'){
        if (Character.isDigit(token))post [j++]=token;
        else if (token =='(')S.push(new NodeData('('));
        else if (token ==')')
            while ((c=S.pop().getData())!='(')post[j++]=c;
        else {
            while (!S.empty() && precedence(S.peek().getData())>= precedence(token))
            post[j++]=S.pop().getData();
           S.push(new NodeData(token));
        }
        token=getToken();
    }
    while (!S.empty())post[j++]=S.pop().getData();
    return j;

}

问题：（1）为什么eclipse告诉我，我的getData（）未定义为类型对象。

我创建的课程：

   public class Node{
    public NodeData data;
    NodeData next;
    public Node(Nodedata d){
        data = d;
        next = null;
    }
     public class NodeData{
     char ch;

    public NodeData(char c){
       ch =c;
   }
   public char getData() {return ch;}

   public int compareTo(NodeData nd){
       if (this.ch ==nd.ch)return 0;
       if (this.ch<nd.ch) return -1;
       return 1;
   }
   public String toString(){
       return ch + " "; //" " needed to convert num to a string
   }
     }
     }

问题：（2）为什么当我尝试编译eclipse时表明NodeData无法解析为某种类型。

Answer 1

SELECT f.*, p.*, COALESCE(p.img, 'profile_images/default.jpg') as profile_img FROM friends f LEFT JOIN profile_img p ON p.user_id = f.friend_one AND p.id = (select max(p2.id) from profile_img p2 where p2.user_id = p.user_id) WHERE f.friend_two = ? AND f.status = ?;方法返回pop中使用的类类型，因此请尝试

栈＆LT; NODEDATA＆GT; stack = new Stack＆lt; NodeData＆gt;（）;

拼写？

旁注：看naming convention

未定义类型对象中缀到后缀

1 个答案: