Adding file contents to an ArrayList; Android

Question

What I am trying to accomplish is to read a file line by line and store each line into an ArrayList. This should be such a simple task but I keep running into numerous problems. At first, it was repeating the lines when it was saved back into a file. Another error which seems to occur quite often is that it skips the try but doesn't catch the exception? I have tried several techniques but no luck. If you have any advice or could provide help in anyway it would be greatly appreciated. Thank you

Current code:

try{
    // command line parameter
    FileInputStream fstream = new FileInputStream(file);
    // Get the object of DataInputStream
    DataInputStream in = new DataInputStream(fstream);
    BufferedReader br = new BufferedReader(new InputStreamReader(in));
    String strLine;

    while ((strLine = br.readLine()) != null)   {
        fileList.add(strLine);
    }
    //Close the input stream
    in.close();
} catch (Exception e){//Catch exception if any
    Toast.makeText(this, "Could Not Open File", Toast.LENGTH_SHORT).show();
}
fileList.add(theContent);

//now to save back to the file
try {
    FileWriter writer = new FileWriter(file); 
    for(String str: fileList) { 
        writer.write(str);
        writer.write("\r\n");
    }
    writer.close();
} catch (java.io.IOException error) {
    //do something if an IOException occurs.
    Toast.makeText(this, "Cannot Save Back To A File", Toast.LENGTH_LONG).show();
}

Egor · Accepted Answer · 2012-07-07 20:37:03Z

2

There is a very simple alternative to what you are doing with Scanner class:

Scanner s = new Scanner(new File("filepath"));
ArrayList<String> list = new ArrayList<String>();
while (s.hasNext()){
    list.add(s.next());
}
s.close();

edited Jul 7, 2012 at 20:37

Egor

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answered Jul 7, 2012 at 20:36

Erol

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3 Comments

chRyNaN Over a year ago

This seems to work for saving the file into an arraylist. However, when trying to save the file back it hits the exception. So, there must be an error with second try block. Also, I would like to be able to do the same thing with another file. But when I try to do the same code, with a different Scanner variable, it force closes.

Matt Wolfe Over a year ago

are you doing this from multiple threads at the same time? What is the exception that is thrown?

The Original Android Over a year ago

@user1478764, You probably got the common error of path/file not valid/exists. Do check for the path/file.

Matt Wolfe · Accepted Answer · 2012-07-07 20:49:55Z

0

Why do you have fileList.add(theContent) after the try/catch? I don't see what the point of that is. Remove that line and see if it helps.

Example, I just tested this code on my local machine (not android but should be the same)

import java.io.*;
import java.util.ArrayList;
class FileRead 
{
 public static void main(String args[])
  {
  ArrayList<String> fileList = new ArrayList<String>();
  final String file = "textfile.txt";
  final String outFile = "textFile1.txt";
  try{
      FileInputStream fstream = new FileInputStream(file);
      DataInputStream in = new DataInputStream(fstream);
      BufferedReader br = new BufferedReader(new InputStreamReader(in));
      String strLine;

      //Read File Line By Line
      while ((strLine = br.readLine()) != null)   {
      // Print the content on the console
        fileList.add(strLine);
      }
      //Close the input stream
      in.close();
    } catch (Exception e){//Catch exception if any
        System.err.println("Error: " + e.getMessage());
    }

   try {
        FileWriter writer = new FileWriter(outFile); 
        for(String str: fileList) { 
          writer.write(str);
          writer.write("\r\n");
        }
        writer.close();
    } catch (java.io.IOException error) {
        System.err.println("Error: " + error.getMessage());
    }
  }
}

After I ran this the 2 files had no differences. So my guess is that line may have something to do with it.

edited Jul 7, 2012 at 20:49

answered Jul 7, 2012 at 20:37

Matt Wolfe

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2 Comments

Egor Over a year ago

It should have been a comment since you're not really answering the question. Please fix this issue.

chRyNaN Over a year ago

the reason for the 'fileList.add(theContent);' is because after all the contents of the file are saved to the arraylist I want to add another value to the arraylist and then re-save it back to a file.

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