Question

嘿我的java程序里面有一个扫描器类，它不会读取文件。它给了我以下例外＆＃34; DayCalParser.java:21：错误：未报告的异常FileNotFoundException;必须被抓住或宣布被扔掉＃34; 我想我应该使用某种IOexception，但不知道放在哪里，因为这只是一个类而且没有主要的方法。

我也收到一条错误，说没有找到退货声明

import java.util.*;
import java.io.*;
import java.lang.*;

public class DayCalParser {
 private int i = 0;
 private String userdate = "";
 private Scanner scan = new Scanner(System.in);
 private int day = scan.nextInt();
 private int fday;
 Scanner fileScan = new Scanner(new File("cal.txt"));
 private ArrayList < String > dates = new ArrayList < String > ();


 private void datesFinder(int fday) throws IOException {

  while (fileScan.hasNext()) {
   String line = fileScan.nextLine();
   if (line.contains("DTSTART")) {
    if (line.length() > 25) {
     String year = line.substring(19, 23);
     String month = line.substring(23, 25);
     String dayofmonth = line.substring(25, 27);
     userdate = (dayofmonth + "/" + month + "/" + year);

    }
   }

   if (line.contains("SUMMARY")) {
    String summary = line.substring(12, 13);
    if (summary.equals(fday)) {
     i = i + 1;
     dates.add(userdate);
    }
   }
  } //while
 }

 public String getDates(int fday) {
  datesFinder(fday);
  for (int j = 0; j < dates.size(); j++) {
   String a = dates.get(j);
   return a;
  }
 }
}

Answer 1

它不是异常，而是编译错误。 Scanner的构造函数抛出FileNotFoundException。在DayCalParser构造函数

中传输初始化

public DayCalParser() throws FileNotFoundException {
    fileScan = new Scanner(new File("cal.txt"));
}

另外，请将getDates()修改为：

public String getDates(int fday) throws IOException {
    datesFinder(fday);
    for (int j = 0; j < dates.size(); j++) {
        String a = dates.get(j);
        return a;
    }
    return null;
}

Answer 2

你可以查看下面的代码，同时修改getDates（）函数，你可以通过任何类调用该函数。

import java.util.*;
import java.io.*;
import java.lang.*;

public class Main {
    private    int i = 0;
    private    String userdate = "";
    private    Scanner scan = new Scanner (System.in);
    private    int day = scan.nextInt();
    private    int fday;
    private    ArrayList<String> dates = new ArrayList<String>();


    private void datesFinder(int fday) throws IOException, FileNotFoundException {
        Scanner fileScan = new Scanner(new File("cal.txt"));
        while (fileScan.hasNext()){
            String line = fileScan.nextLine();
            if (line.contains("DTSTART")){
                if (line.length()>25){
                    String year = line.substring(19,23);
                    String month = line.substring(23,25);
                    String dayofmonth = line.substring(25,27);
                    userdate = (dayofmonth + "/" + month + "/" + year);

                }
            }

            if (line.contains("SUMMARY")) {
                String summary = line.substring(12,13);
                if (summary.equals(fday)){
                    i = i+1;
                    dates.add(userdate);
                }
            }
        }//while
    }

    public String getDates(int fday){
        try {
            datesFinder(fday);
            for(int j = 0; j < dates.size(); j++) {
                String a = dates.get(j);
                return a;
            }
        }catch (IOException e){
          e.printStackTrace();
        }
        return null;
    }

    public static void main(String[] args) {
        Main obj = new Main();
        obj.getDates((int) (new Date().getTime()/1000));
    }
}

扫描仪类不读取文件

2 个答案: