Slide 5.18: Files and I/O (cont.): Reading a file

Slide 5.17: Files and I/O (cont.): Writing to a file
Slide 5.a: Populating and updating an ArrayList
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Files and I/O (Cont.)

Reading a File
In the following example, we use the Scanner class to read the contents of the text file we created in the previous example:

ReadFile.java (reading a file)

 import java.io.File;
 import java.io.FileNotFoundException;
 import java.util.Scanner;

 public class ReadFile {
   public static void main( String[ ] args ) {
     try {
       File myObj = new File( args[0] );
       Scanner myReader = new Scanner( myObj );
       while ( myReader.( ) ) {
         String data = myReader.( );
         System.out.println( data );
       }
       myReader.close( );
     }
     catch ( FileNotFoundException e ) {
       System.out.println( "An error occurred." );
       e.printStackTrace( );
     }
   }
 }

shell> java ReadFile

Some of the file classes are given next (cont.):

FileWriter, which is used for writing streams of characters

BufferedWriter, which writes text to a character-output stream, buffering characters so as to provide for the efficient writing (better performance) of single characters, arrays, and strings

FileOutputStream, which is useful to read data from a file in the form of sequence of bytes

Slide 5.17: Files and I/O (cont.): Writing to a file
Slide 5.a: Populating and updating an ArrayList
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