从Java中的文本文件读取字符串

Question

我正在为我的编程期末考试而学习。 我必须编写一个程序来打开一个存储在字符串fileName中的文件，并在文件中查找一个名为personName的字符串，这应该在personName之后打印第一个字符串，然后该程序应该在打印后终止，如果参数personName是不在文件中，则应打印“此名称不存在”，然后，如果发生IOException，则应打印“存在IO错误”，程序应使用system.exit（0）退出

程序应使用文件info.txt，每行应包含两个字符串，第一个字符串名称和第二个年龄。

一切都必须合而为一

data.txt包含

最高60.0

乔19.0

阿里20.0

到目前为止，我的代码是：

public class Files{

    public void InfoReader(String fileName, String personName)
    {

      try{
         try{
                   // Open the file that is the first 
                  // command line parameter
                  FileInputStream fstream = new FileInputStream("C://rest//data.txt");
                  // Get the object of DataInputStream

                  DataInputStream in = new DataInputStream(fstream);
                  BufferedReader br = new BufferedReader(new InputStreamReader(in));

                  //Read File Line By Line
                  while ((fileName = br.readLine()) != null) {
                      // Print the content on the console
                      (new Files()).infoReader("info.txt","Joe"); //this prints the age
                  }
                  //Close the input stream
                  in.close();
              }

              catch (IOException e)
              {//Catch exception if any
                    System.out.println(" there is an IO Error");
                    System.exit(0);
              }
     }
    catch (Exception e)
              {//Catch exception if any
                    System.out.println("that name doesn't exists");

              }
    }
}

infoReader(info.txt,Joe); 应该打印19.0
但是我收到一个java.lang.StackOverflowError

任何帮助将非常感激！！

提前致谢！

Answer 1

这就是我想您正在尝试做的。 如果没有，至少可以作为示例。 就像amit提到的那样，您当前的错误是由于递归调用引起的，我认为这是不必要的。

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class Files {

    public void InfoReader(String fileName, String personName) {
        try {
            // Open the file that is the first command line parameter
            FileInputStream fstream = new FileInputStream(fileName);

            // Get the object of DataInputStream
            DataInputStream in = new DataInputStream(fstream);
            BufferedReader br = new BufferedReader(new InputStreamReader(in));

            String line = null;

            //Loop until there are no more lines in the file
            while((line = br.readLine()) != null) {
                //Split the line to get 'personaName' and 'age'.
                String[] lineParts = line.split(" ");

                //Compare this line personName with the one provided
                if(lineParts[0].equals(personName)) {
                    //Print age
                    System.out.println(lineParts[1]);
                    br.close();
                    System.exit(0);
                }
            }

            br.close();
            //If we got here, it means that personName was not found in the file.
            System.out.println("that name doesn't exists");
        } catch (IOException e) {
            System.out.println(" there is an IO Error");
        }
    }
}

Answer 2

如果您使用Scanner类，它将使您的生活变得更加轻松。

  Scanner fileScanner = new Scanner (new File(fileName));

  while(fileScanner.hasNextLine()
   {
      String line = fileScanner.nextLine();

      Scanner lineScanner = new Scanner(line);

      String name = lineScanner.next(); // gets the name
      double age  = Double.parseDouble(lineScanner.next()); // gets the age

      // That's all really! Now do the rest!
   }

Answer 3

使用commons-io，不要忘记编码！

List<String> lines = FileUtils.readLines(file, encoding)