java中编译错误：找不到符号。 [英] Compile error in java :cannot find symbol.

问题描述

我有这样的代码，它是一个文本文件，并把它变成一个字符串，然后将字符串的部分分成一个数组列表的不同元素。

I have this code that is taking a text file and turning it into a string and then separating parts of the string into different elements of an arraylist.

import java.util.Scanner;
import java.io.*;
import java.util.ArrayList;

public class Grocery{

    public Grocery(){

        File inFile = new File ("lists.txt");
        Scanner input = new Scanner (inFile);
        String grocery;
        {
             grocery = input.nextLine();
        }
    }

    public void makeSmallerLists(){
        String listLine;
        String line;
        ArrayList<String> smallList = new ArrayList<String>();
        while(input.hasNextLine()){
            line = input.nextLine;
            if(line.equals("<END>")){
                smallList.add(listLine);
            } else{
                listLine = listLine + "\n" + line;
            }
        }
    }
}

当我尝试编译这会给我两个错误：

However when I try to compile this it gives me two errors:

javac Message.java Message.java:31：找不到符号符号：
变量输入位置：类消息while（input.hasNextLine（））{
^ Message.java:32：找不到符号符号：变量输入位置：class消息行= input.nextLine;
^

javac Message.java Message.java:31: cannot find symbol symbol : variable input location: class Message while(input.hasNextLine()){ ^ Message.java:32: cannot find symbol symbol : variable input location: class Message line = input.nextLine; ^

如何解决这个问题？我真的不知道是什么问题。

How do I fix this? I really don't know what's wrong.

我修复了，现在我的错误说
$ javac Message.java
Message.java:34 ：找不到符号
symbol：variable nextLine
location：class java.util.Scanner
line = input.nextLine;
^

I fixed that and now my error says $ javac Message.java Message.java:34: cannot find symbol symbol : variable nextLine location: class java.util.Scanner line = input.nextLine; ^

           ^

现在有什么问题？

推荐答案

 Scanner input = new Scanner (inFile);

输入是构造函数的本地无法访问其外部，并且您尝试在 makeSmallerLists（）方法中访问。使它成为一个实例成员，以便通过类而不是 static 上下文可用。

input is local to the constructor, you cannot access outside of it, and you are trying to access in makeSmallerLists() method. Make it as a instance member, So that it available through out the class other than static context.

public class Grocery{

  Scanner input;

和构造函数

public Grocery(){

            File inFile = new File ("lists.txt");
             input = new Scanner (inFile);

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