FileIO

[sumit kothalikar]

//Date 22/06/2010
Programmer : Sumit Kothalikar

  

import java.io.*;
class BufferedWR{
public static void main(String [] args){

String s;
try{
File f = new File("Shree.txt");
FileWriter fw = new FileWriter(f);
BufferedWriter bw = new BufferedWriter(fw); 
bw.write(" hello how are u  what is your name "); //line 1
 
FileReader fr = new FileReader(f);
BufferedReader br = new BufferedReader(fr);

s = br.readLine();// line 2
while(s!=null){  // line 3
System.out.println(" file data " +s);  // line 4
}
br.close();
bw.close();
} catch(IOException e){}
} 
}


  

line 1 writes the quoted text in Shree.txt file
even though the text is read at line 2 it worksout to be that s is null at line 3 and
there is no output
my question is why s becomes null at line 3 what should be done to read Shree.txt file

[Tom Reilly]

Line 1 writes your text to the BufferedWriter - not the file. You need to call flush() and/or close() to write the text to the file. Then you can read it. Try moving bw.close() to just after line 1.

[sumit kothalikar]

  



 import java.io.*;  
 class BufferedWR{  
 public static void main(String [] args){  
   
 String s;  
 try{  
 File f = new File("Shree.txt");  
 FileWriter fw = new FileWriter(f);  
 BufferedWriter bw = new BufferedWriter(fw);   
 bw.write(" hello how are u  what is your name "); //line 1  
    bw.close();  // line new
 FileReader fr = new FileReader(f);  
 BufferedReader br = new BufferedReader(fr);  
   
 s = br.readLine();// line 2  
 while(s!=null){  // line 3  
 System.out.println(" file data " +s);  // line 4  
 }  
 br.close();  
 
 } catch(IOException e){}  
 }   
 }  
     

Sir,
I did it as you said in line new but the program goes into infinite loop after running the above code.
I can't understand why is it happening so.

[Tom Reilly]

You are initializing s properly but not updating it in your loop so s is never being set to null. Try adding

s = br.readLine();

to your while loop.

[sumit kothalikar]

  
 import java.io.*;    
  class BufferedWR{    
  public static void main(String [] args){    
      
  String s;    
  try{    
  File f = new File("Shree.txt");    
  FileWriter fw = new FileWriter(f);    
  BufferedWriter bw = new BufferedWriter(fw);     
  bw.write(" hello how are u  what is your name "); //line 1    
     bw.close();  // line new  
  FileReader fr = new FileReader(f);    
  BufferedReader br = new BufferedReader(fr);    
      
  s = br.readLine();// line 2    
  while((s=br.readLine())!=null){  // line 3    
  System.out.println(" file data " +s);  // line 4    
  }    
  br.close();    
    
  } catch(IOException e){}    
  }     
    

I changed the while code at line 3
but now it doesn't print anything.

[Tom Reilly]

I think we've now fallen into the trap where you ask a follow-up question without first thinking it through yourself. Your problem now is not a misunderstanding about how an API works. It is a simple bug in your code.

[Ulf Dittmer]

Never do this:

} catch(IOException e){}    
} 

You simply must handle IO exceptions; at least print a message to the log or system out so you know something bad happened.

[Abimaran Kugathasan]

Let's help him

import java.io.*;

public class BufferedWR{
  public static void main(String [] args){

  	String s;
  	try{
  		File f = new File("Shree.txt");
  		FileWriter fw = new FileWriter(f);
  		BufferedWriter bw = new BufferedWriter(fw);
  		bw.write(" hello how are u  what is your name ");
     	bw.close();
  		FileReader fr = new FileReader(f);
  		BufferedReader br = new BufferedReader(fr);

  		while((s=br.readLine())!=null){
  			System.out.println(" file data : " +s);
  		}
  		br.close();

  		}
  		catch(IOException e){
			e.printStackTrace();
		}
  }
}

Check this....

[sumit kothalikar]

Never do this:

catch(IOException e){}


catch(IOException e){} }
You simply must handle IO exceptions; at least print a message to the log or system out so you know something bad happened.

Yes i got it what you want to say Sir
i will always include a System.out.println(e) statement in catch block to through the exception.

But please tell me is there any bug in my code
i am not getting why it is not printing the text which i am writing to the file Shree.txt.

[Abimaran Kugathasan]

sumit kothalikar wrote:

  
 import java.io.*;    
  class BufferedWR{    
  public static void main(String [] args){    
      
  String s;    
  try{    
  File f = new File("Shree.txt");    
  FileWriter fw = new FileWriter(f);    
  BufferedWriter bw = new BufferedWriter(fw);     
  bw.write(" hello how are u  what is your name "); //line 1    
     bw.close();  // line new  
  FileReader fr = new FileReader(f);    
  BufferedReader br = new BufferedReader(fr);    
      
  s = br.readLine();// line 2    
  while((s=br.readLine())!=null){  // line 3    
  System.out.println(" file data " +s);  // line 4    
  }    
  br.close();    
    
  } catch(IOException e){}    
  }     
    

I changed the while code at line 3
but now it doesn't print anything.

Try this code, I made a correction,

 import java.io.*;
  public class BufferedWR{
  public static void main(String [] args){

  String s;
  try{
  File f = new File("Shree.txt");
  FileWriter fw = new FileWriter(f);
  BufferedWriter bw = new BufferedWriter(fw);
  bw.write(" hello how are u  what is your name "); //line 1
     bw.close();  // line new
  FileReader fr = new FileReader(f);
  BufferedReader br = new BufferedReader(fr);

  s = br.readLine();// line 2
  System.out.println(s); // made a correction here, can you guess?
  while((s=br.readLine())!=null){  // line 3
  System.out.println(" file data " +s);  // line 4
  }
  br.close();

  } catch(IOException e){}
  }
}

Clue: readLine() method read& returns the next line in your text.

[sumit kothalikar]

thank you Abimaran Kugathasan Sir

[Abimaran Kugathasan]

No need of Sir!

[sumit kothalikar]

ok thanks Abimaran