获取java.lang.string从未使用过的错误

Question

谁能解释我为什么收到此错误？ 不只是这个

从未使用构造函数“ StockMachine（java.lang.String）”

但也有人说从未使用过Method。 我不确定为什么会这样。 这是我的代码片段：

import java.io.*;
import java.util.*;
import java.io.FileInputStream;

public class StockMachine {

    private StockPriceService [] stockPriceServices;

    private String tickerSymbols[];

    private final int NUMBEROFSERVICES = 3;

    public StockMachine(String fileName) {
        stockPriceServices = new StockPriceService[3];
        stockPriceServices[0] = new UHStockService();
        stockPriceServices[1] = new NLPService();
        stockPriceServices[2] = new ExternalService();
        try {
            FileInputStream fis = new FileInputStream(fileName);
            Scanner scan = new Scanner(fis);
            this.tickerSymbols = new String[scan.nextInt()];
            int i = 0;
            while (scan.hasNext()) {
                this.tickerSymbols[i] = scan.next();
                i++;
            }
        }

        catch (FileNotFoundException e) {
            e.printStackTrace();
        }

    }
}