我正在做一个CSV阅读器，但我得到了一个NullPointerException它说：java.lang.NullPointerException:无法调用“java.util.Scanner.nextLine（）”，因为“this.s”在csvReader.（csvReader.java：23）的csvReader.scanner（csvReader.java：34）中为null。
以下是我目前为止的代码：

import java.util.Scanner;
import java.util.NoSuchElementException;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.StringTokenizer;
/**
 * Write a description of class csvReader here.
 *
 * @author (your name)
 * @version (a version number or a date)
 */
public class csvReader
{
    // instance variables - replace the example below with your own
    private int x;
    private Scanner s;
    private static StringTokenizer tokenizer;
    /**
     * Constructor for objects of class csvReader
     */
    public csvReader()
    {
        scanner();
    }

    private static String[] getTokens (String input) {
        String[] tokens = new String[5];
        // Create empty String in each of 5 locations so
        // I can add to them
        for (int i = 0; i < tokens.length; i++){
            tokens[i] = "";
        }
    
        int index = 0; // location in array
        int pointer = 0; // location in the String
        boolean inQuotes = false; // to keep track of whether the pointer
        // within quotes - ignore commas
        while (true){
            if (pointer == input.length()){
                break;
            }
            if (input.charAt(pointer) == '\"'){
                if (inQuotes){      
                    inQuotes = false;
                } else {
                    inQuotes = true;
                }
            }
            else if (input.charAt(pointer) == ','){
                if (inQuotes){ // while between quotes
                    // commas get added at end of current token
                    tokens[index] += input.charAt(pointer);
                } else {
                    // when not in quotes, comma means move on
                    // to next token
                    index++;
                }
            }
            else {
                // anything other than " or , will get added to the end
                // of my current token.
                tokens[index] += input.charAt(pointer);
            }
            pointer++;
        }
    
        return tokens;
    }
    
    public void scanner()
    {
        boolean moreLines = true;
        int numTransactions = 0;
        while (moreLines)
        {
            try
            {
                System.out.println(s.nextLine());
                numTransactions++;
            }
            catch (NoSuchElementException e)
            {
                moreLines = false;
                System.out.println("There are " + numTransactions + "transactions");
            }
        }
        
        try {
            s = new Scanner (new File ("visadata.txt"));
        }
        catch (FileNotFoundException e)
        {
            System.out.println("File Not Found");
        } 
    }
}

我做错了什么？
我想让扫描仪告诉我总共有多少笔交易，借记和贷记交易的数量，以及所有借记交易的总数。我现在正忙着查找事务总数，但我得到了一个NullPointerException