Question

Here is my source code. I got the reading part but need a simple logic for my writing part which I”m not getting. Here in my current logic, data gets overwritten and I’m always able to see the last block of read data in my written file.

import java.io.File;
import java.io.FileInputStream;
java.io.FileNotFoundException;
java.io.FileOutputStream;
import java.io.IOException;
public class LoadTest 
 {  
public void readFiles(File file) throws FileNotFoundException
       {
        int fsize = (int) file.length();
        int part = (fsize/4)+(fsize%4);
        byte[] block = new byte[part]; 
        FileInputStream fin = new FileInputStream(file);
        try
        {
            int val=-1;
            do
            {
                int bytesread =0;
                while(bytesread<part)
                    {
                        val = fin.read(block, bytesread, part-bytesread);
                        if (val<0)
                            break;
                        bytesread += val;

                    }
                writeFiles(block,bytesread);                            
            }
            while(val>=0);
            fin.close();
        }
        catch(IOException e)
        {
            e.printStackTrace();
        }

    }
public void writeFiles(byte[] block, int len) throws IOException
{
    int byteswritten = 0;
    FileOutputStream fout = new FileOutputStream("input.csv");
    fout.write(block, byteswritten, len+byteswritten);
    byteswritten +=len;
    fout.close();
}


public static void main(String[] args) throws FileNotFoundException
{  
    LoadTest testobj = new LoadTest();
    String folder = "/Users/NiranjanSubramanian/Desktop/TestFiles";
    File dir = new File(folder);
    File[] files = dir.listFiles();
    System.out.println("Started");
    for( File entry: files)
    {  
        testobj.readFiles(entry);

    }
    System.out.println("Ended");

}

}

Answer 1

See my comments for how to solve the issue in a simple manner. However, let me suggest to you a simple alternative to do what you’re asking.

final Path dir = Paths.get("/Users/NiranjanSubramanian/Desktop/TestFiles");
try (final OutputStream out = Files.newOutputStream(Paths.get("input.csv"))) {
  for (final Path file : Files.newDirectoryStream(dir)) {
    Files.copy(file, out);
  }
}

This relies on Java 7’s new file API but is (at least in my opinion) a far cleaner solution.