files

[abalfazl hossein]

public class Main {


    public static void main(String[] args) throws IOException{
     

      FileInputStream in = null;
        FileOutputStream out = null;
        try {
            in = new FileInputStream("myfile1.txt");
            out = new FileOutputStream("myfile1.txt");
            int c;

            while ((c = in.read()) != -1) {
                out.write(c);
            }

        } finally {
            if (in != null) {
                in.close();
            }
            if (out != null) {
                out.close();
            }
        }
    }

}

I open myfile1 in windows, I write blah blah blah...

But when I run this program it does not print out. and after that when I open again, I see the file is empty. Why?

[Mohamed Sanaulla]

If the file is already existing- Try using only Reading the file. Because if you open the stream for writing to the file- The contents will get erased provided you are not trying to append the contents to the file.

[Henry Wong]

Mohamed Sanaulla wrote:The contents will get erased provided you are not trying to append the contents to the file.

Agreed. Line 11 will truncate the file.

Henry

[abalfazl hossein]

then it is a mistake of sun web site:

http://download.oracle.com/javase/tutorial/essential/io/bytestreams.html

How can I report them to fix it?

[Henry Wong]

abalfazl hossein wrote:
How can I report them to fix it?

There is nothing wrong with the Sun / Oracle code. It's your version that broken -- as you use the same filename for both the in and out file.

Henry

[Mohamed Sanaulla]

abalfazl hossein wrote:then it is a mistake of sun web site:

http://download.oracle.com/javase/tutorial/essential/io/bytestreams.html

How can I report them to fix it?

its correctThe program is correct. They are using 2 different files to copy the content.

[abalfazl hossein]

Now this error

Exception in thread "main" java.lang.NullPointerException
at filetestread.Main.main(Main.java:36)
Java Result: 1

[Mohamed Sanaulla]

abalfazl hossein wrote:Now this error

Exception in thread "main" java.lang.NullPointerException
at filetestread.Main.main(Main.java:36)
Java Result: 1

There is no Line 36 in the code you have posted. Can you post the updated code you are using where you found this exception?

[abalfazl hossein]

package filetestread;



import java.io.*;
/**
 *
 * @author Administrator
 */
public class Main {


    public static void main(String[] args) throws IOException{
     

      FileInputStream in = null;
        FileOutputStream out = null;
        try {
            in = new FileInputStream("myfile1.txt");
            //out = new FileOutputStream("myfile1.txt");
            int c;

            while ((c = in.read()) != -1) {
                out.write(c);
            }

        } finally {
            if (in != null) {
                in.close();
            }
            if (out != null) {
                out.close();
            }
        }
    }

}

run:
Exception in thread "main" java.lang.NullPointerException
at filetestread.Main.main(Main.java:29)
Java Result: 1
BUILD SUCCESSFUL (total time: 0 seconds)

[Mohamed Sanaulla]

At line 20 you have commented out the instantiation of the FileOutputStream. So out is null and at line 24 you are trying to use a null value. So it should throw a java.lang.NullPointerException

But I dont understand why its giving java.lang.NullPointerException at line 29.

[Henry Wong]

Mohamed Sanaulla wrote:
But I dont understand why its giving java.lang.NullPointerException at line 29.

Probably the OP not providing all the lines in the file. Next time it may be a good idea to bring up the text editor, find line 29, and tell us which line it is -- as it may not be the same if you don't provide all of the file.

Henry

[abalfazl hossein]

 while ((c = in.read()) != -1) 

This line has problem

The whole code:

import java.io.*;
/**
 *
 * @author Administrator
 */
public class Main {


    public static void main(String[] args) throws IOException{
     

      FileInputStream in = null;
        FileOutputStream out = null;
        try {
            
            out = new FileOutputStream("myfile1.txt");
            int c;

            while ((c = in.read()) != -1) {
                out.write(c);
            }

        } finally {
            if (in != null) {
                in.close();
            }
            if (out != null) {
                out.close();
            }
        }
    }

}

I have a text file I want read it and show the content by byte stream

[Mohamed Sanaulla]

abalfazl hossein wrote:

 while ((c = in.read()) != -1) 

This line has problem

it has problem because You haven't initialized the in reference to a valid FileInputStream reference. Please note that unless you initialize the object references with valid instances/objects you cannot use those references.

[abalfazl hossein]

public class Main {


    public static void main(String[] args) throws IOException{
     

        FileInputStream in = null;
        //FileOutputStream out = null;
        try {
            
            in = new FileInputStream("myfile1.txt");
            int c;

            while ((c = in.read()) != -1) {
                System.out.print(c);
               // out.write(c);
            }

        } finally {
            if (in != null) {
                in.close();
            }
           // if (out != null) {
               // out.close();
            }
        }
   // }

}

The output is:

1039710310011510310011510311597100103100115103100115103100115103100115103100115103100115103

Now, I want to see the contents as the character, How can I do this?

[Mohamed Sanaulla]

You might want have to explore classes like Scanner, BufferedReader for the same.

[Wouter Oet]

Or go through the Basic I/O tutorial.

[abalfazl hossein]

If I save this string in a text file, Is it possible to cover it to char? by FileOutputStream?


http://download.oracle.com/javase/tutorial/essential/io/bytestreams.html

[Mohamed Sanaulla]

abalfazl hossein wrote:If I save this string in a text file, Is it possible to cover it to char? by FileOutputStream?


http://download.oracle.com/javase/tutorial/essential/io/bytestreams.html

Did you try executing the example- After all the suggestions given above? It would be helpful if you could understand and execute that sample.

[abalfazl hossein]

InputStreamReader i = new InputStreamReader (new FileInputStream("myfile1.txt"),"Cp1256"));

Is it possible to read char without using any other class in this code? and without typecast?