A program to demonstrate simple text-based input and output in Java.

SimpleFileIO.java

/**
 * Simple File IO
 * 
 * A program to demonstrate simple text-based input and output in Java.
 * 
 * This version uses PrintStream, the same class as System.out.  An
 * alternative implementation would be to use the PrintWriter class.
 * 
 * @author jtk
 * 
 * @date 2/21/2013
 */
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintStream;

public class SimpleFileIO {
    public static void main(String[] args) {
        Scanner scanner = null;
        PrintStream ps = null;

        // Specify the input File and create a Scanner object for it...
        File in = new File("input.txt");
        try {
            scanner = new Scanner(in);
        } catch (FileNotFoundException e) {
            e.printStackTrace();  // just print an error stack trace
        }
        
        // Specify the output File and create a PrintStream object for it...
        File out = new File("output.txt");
        try {
            ps = new PrintStream(out);
        } catch (FileNotFoundException e) {
            e.printStackTrace();  // just print an error stack trace
        }
        
        // Loop reading lines, processing (trivially), and writing...
        while (scanner.hasNextLine()) {
            String s = scanner.nextLine();
            s = s.toUpperCase();
            ps.println(s);
        }
        
        // Close the output file to flush internal buffers...
        ps.close();
    }
}