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readChar() method and EOF exception

Posted on 2002-03-21
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Last Modified: 2010-05-18
I am a CS major and am trying to improve on my programming skills, but I have come across a roadblock. I am using the readChar() method to read characters one by one from a specified file and almost everything is going smoothly except that I am not sure on the most efficient way to let my program know it has reached the end of a file. I am trying to use the End Of File execption, but it still reads on forever. I pasted my code here for an illustration. Any pointers?

- Alex


import java.io.*;

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

     if (args.length < 1){
         System.out.println("Program syntax: java FileDemo FILE.XXX");
         System.exit(1);
     }

     DataInputStream in = new DataInputStream(
                          new FileInputStream(args[0]));

     InputStreamReader isr = new InputStreamReader(in);


     System.out.println("<<Start of file>>");


     try {
         char newChar = (char) isr.read();
         while(true) {
          System.out.print(newChar);
          newChar = (char) isr.read();
         }
     } catch (EOFException e) { }
     in.close();
     
     System.out.println("<<End of file>>");    
    }
}
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Question by:alrav79
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6 Comments
 
LVL 4

Accepted Solution

by:
m_onkey_boy earned 150 total points
ID: 6887452
int c;
while ((c = isr.read()) != -1) {
  System.out.println((char)c);
}
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LVL 4

Expert Comment

by:m_onkey_boy
ID: 6887462
BTW - in your example, DataInputStream is not adding anything to your program other than overhead.
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Author Comment

by:alrav79
ID: 6887479
what do you mean overhead?
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Author Comment

by:alrav79
ID: 6887507
could have explained the process a litte more
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LVL 4

Expert Comment

by:m_onkey_boy
ID: 6888103
You didn't give me a chance to elaborate - you could have asked.

OK:

What I meant by overhead was that by using the datainputstream, you have instantiated an object tha was not needed.  Also, each call to read() is being passed up an extra method call (InputStreamReader.read() calls DataInputStream.read(), which in turn calls FileInputStream.read()).  Why not cut out the middleman?

As far as explaining the process - the code is self-explanatory.  I guess the part you should notice is that -1 is the EOF marker in a Java stream.
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Author Comment

by:alrav79
ID: 6888508
sorry, man, that was my fault....thanks for the explanation though; it was very helpful
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