Copying the Contents of One text file to Another i

Question

I am trying to copy the contents of one text file ("1.txt") which contains 2-3 integer numbers (ex: 1 2 3) to another text file ("2.txt") but I am getting the following error upon compilation

import java.io.*;
class FileDemo {
    public static void main(String args[]) {
      try {
          FileReader fr=new FileReader("1.txt");
          FileWriter fw=new FileWriter("2.txt");
          int c=fr.read();
          while(c!=-1) {
            fw.write(c);
          }
      } catch(IOException e) {
          System.out.println(e);
      } finally() { 
          fr.close();
          fw.close();
      }
    }
}

Command prompt:-

C:\Documents and Settings\Salman\Desktop>javac FileDemo.java
FileDemo.java:20: error: '{' expected
                finally()
                       ^
FileDemo.java:20: error: illegal start of expression
                finally()
                        ^
FileDemo.java:20: error: ';' expected
                finally()
                         ^
FileDemo.java:27: error: reached end of file while parsing
}
 ^
4 errors

But upon checking the code, I find that the finally() block is properly closed.

Answer 1

public class Copytextfronanothertextfile{

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

        FileReader fr = null;
        FileWriter fw = null;

        try{
        fr = new FileReader("C:\\Users\\Muzzammil\\Desktop\\chinese.txt");
        fw = new FileWriter("C:\\Users\\Muzzammil\\Desktop\\jago.txt");


        int c;
        while((c = fr.read()) != -1){
            fw.write(c);

        }


    }finally{

           if (fr != null){ 
            fr.close();
        }

           if(fw != null){

              fw.close();
           }
}

}

}

Answer 2

A Finally block shouldn't have the round parentheses.

Try:

import java.io.*;
class FileDemo
{
    public static void main(String args[])
    {
        try
        {
            FileReader fr=new FileReader("1.txt");
            FileWriter fw=new FileWriter("2.txt");
            int c=fr.read();
            while(c!=-1)
            {
                fw.write(c);
                c = fr.read(); // Add this line
            }
        }
        catch(IOException e)
        {
            System.out.println(e);
        }
        finally
        {   
            fr.close();
            fw.close();
        }

    }
}

Answer 3

Try this code:

class CopyContentFromToText {

    public static void main(String args[]){      

        String fileInput = "C://Users//Adhiraj//Desktop//temp.txt";
        String fileoutput = "C://Users//Adhiraj//Desktop//temp1.txt";
        try {
            FileReader fr=new FileReader(fileInput);
            FileWriter fw=new FileWriter(fileoutput);

            int c;
            while((c=fr.read())!=-1) {
                fw.write(c);
            } 
            fr.close();
            fw.close();

        } 
        catch(IOException e) {
            System.out.println(e);
        } 
     }
}

Answer 4

import java.io.*;
class FileDemo 
{
public static void main(String args[])throws IOException
{
    FileReader fr=null;
    FileWriter fw=null;
  try 
  {
      fr=new FileReader("1.txt");
      fw=new FileWriter("2.txt");
      int c=fr.read();
      while(c!=-1) 
      {
        fw.write(c);
      }
  } 
  catch(IOException e) 
  {
      System.out.println(e);
  } 
  finally
  { 
      fr.close();
      fw.close();
  }
}
}

1.your code is not correct > finally block does not takes parenthesis ahead if it. 2.parenthesis always comes in front of methods only. 3.dear your Scope of FileReader and FileWrier objects are end with in the try blocks so you will get one more error in finally block that is fw not found and fr not found 4."throws IOEXception" also mention front of main function

Answer 5

It's finally, not finally():

try {
    //...
} catch(IOException e) {
    //...
} finally {
    //...
}

By the way, you have an endless loop there:

int c=fr.read();
while(c!=-1) {
    fw.write(c);
}

You must read the data inside the loop in order to let it finish:

int c=fr.read();
while(c!=-1) {
    fw.write(c);
    c = fr.read();
}

In the finally block, your fr and fw variables can't be found since they're declared in the scope of the try block. Declare them outside:

FileReader fr = null;
FileWriter fw = null;
try {
    //...

Now, since they are initialized with null value, you must also do a null check before closing them:

finally {
    if (fr != null) {
        fr.close();
    }
    if (fw != null) {
        fw.close();
    }
}

And the close method on both can throw IOException that must be handled as well:

finally {
    if (fr != null) {
        try {
            fr.close();
        } catch(IOException e) {
            //...
        }
    }
    if (fw != null) {
        try {
            fw.close();
        } catch(IOException e) {
            //...
        }
    }
}

In the end, since you don't want to have a lot of code to close a basic stream, just move it into a method that handles a Closeable (note that both FileReader and FileWriter implements this interface):

public static void close(Closeable stream) {
    try {
        if (stream != null) {
            stream.close();
        }
    } catch(IOException e) {
        //...
    }
}

In the end, your code should look like:

import java.io.*;
class FileDemo {
    public static void main(String args[]) {
        FileReader fr = null;
        FileWriter fw = null;
        try {
            fr = new FileReader("1.txt");
            fw = new FileWriter("2.txt");
            int c = fr.read();
            while(c!=-1) {
                fw.write(c);
                c = fr.read();
            }
        } catch(IOException e) {
            e.printStackTrace();
        } finally {
            close(fr);
            close(fw);
        }
    }
    public static void close(Closeable stream) {
        try {
            if (stream != null) {
                stream.close();
            }
        } catch(IOException e) {
            //...
        }
    }
}

Since Java 7, we have try-with-resources, so code above could be rewritten like:

import java.io.*;
class FileDemo {
    public static void main(String args[]) {
        //this will close the resources automatically
        //even if an exception rises
        try (FileReader fr = new FileReader("1.txt");
             FileWriter fw = new FileWriter("2.txt")) {
            int c = fr.read();
            while(c!=-1) {
                fw.write(c);
                c = fr.read();
            }
        } catch(IOException e) {
            e.printStackTrace();
        }
    }
}

Answer 6

Its a compilation error

public static void main(String args[])
    {
        try
        {
            FileReader fr=new FileReader("1.txt");
            FileWriter fw=new FileWriter("2.txt");
            int c=fr.read();
            while(c!=-1)
            {
                fw.write(c);
            }
        }
        catch(IOException e)
        {
            System.out.println(e);
        }
        finally // finally doesn't accept any arguments like catch
        {   
            fr.close();
            fw.close();
        }

    }