DataOutputStream.write(int b) doesn't write

Question

i'm writing a java program in eclipse that take a file as input and write a new file as output follow some logic.

i use datainputstream for the input file and dataoutputstream for the output file. i use those for the readln() method that works well.

now i have a problem with the write() method, simply it doesn't write anything! i've tryed also randomAccess for the input, and/or bufferedoutputstream for the output.

i've tryed in a separate java project this:

public static void main (String[] args){

    File output = new File("MyOutputDirectoryHere");

    try{
        DataOutputStream  dos = new DataOutputStream(new     BufferedOutputStream(new FileOutputStream (output)));
        for(int i=0; i<1000; i++){
            dos.write(i);
        }
        dos.close();
    }
    catch (IOException e){
        System.err.println(e);
    }   
}

and it works perfectly

but inside this mess:

import java.io.*;
import javax.swing.*;

public class apri_file {        
@SuppressWarnings("deprecation")
public static void main(String[] args){
    File inputFile = null;
    File outputFile = null;
    String dati;
    int dato;

    try {
        JFileChooser FileWindow = new JFileChooser();
        FileWindow.isDirectorySelectionEnabled();

        FileWindow.setApproveButtonText("Open IPL File");
        if(FileWindow.showOpenDialog(null) == JFileChooser.APPROVE_OPTION){
            inputFile = FileWindow.getSelectedFile();
            System.out.println("input path: " + inputFile.getAbsolutePath());
        }

        DataInputStream in = new DataInputStream( new BufferedInputStream( new FileInputStream(inputFile)));
        System.out.println("input buffer reader created");
        /**************************/

        FileWindow.setApproveButtonText("Save PLY FIle");
        if(FileWindow.showSaveDialog(null) == JFileChooser.APPROVE_OPTION){
            outputFile = new File (FileWindow.getSelectedFile(),"");
            System.out.println("output path: " + outputFile.getAbsolutePath());
        }

        DataOutputStream  out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream (outputFile)));
        /**************************/

        /*
         * to do write header
         */
        for(int i=0;i<inputFile.length();i++){
            dati = in.readLine();
            if(dati == null){
                break;
            }
            if(dati == "vnod"){
                while(in.read() != 0X65){
                    dato = in.read();
                    if(dato == 0X09 || dato == 0X0D || dato == 0X2C){   }
                    else if(dato == 0X2E) out.write(0X2C);                      
                    else out.write(dato);
                }
            }
            if(dati == "link"){
                int virgola = 0;
                dato = in.read();
                while(dato != 0X65){
                    if(virgola < 4){
                        if(dato == 0X2C) virgola++;
                        if(dato == 0X09 || dato == 0X0D){}
                        else out.write(dato);
                    }
                    else{
                        while(dato != 0X0D) {
                            dato = in.read();
                        }
                        virgola = 0;
                        out.write(0X0D);//nl
                        out.write(0X34);//4
                        out.write(0X20);//space
                    }
                    dato = in.read();

                }//while link
                end = true;
            }//if link
        }//while file

                    //testing the write() method
        for(int i=0; i<1000; i++){
            out.write(0X2C); //tricky part! this output will be always written!! WTF!
        }
        in.close();
        out.close();

        JOptionPane.showMessageDialog(null, "Done!", "Done!" , JOptionPane.INFORMATION_MESSAGE);            
    }
    catch (IOException e){
        System.out.println(e + "\n");
    }
}
}

in the code above the write(int b) method doesn't write anything in my output file on desktop, except for the for loop coded at the end... that part of code works well...

i dont know what to do. please help.

Answer 1

In java, you cannot compare strings using ==. You have to use equals()

if (dati.equals("vnod")) ...

The == just compare the reference (like a pointer) of equalness and not it's referenced content.

See also here.

Answer 2

You should close all your streams in finally blocks. Clearly the output stream isn't being closed here.