Ioproov.java

// Vaike demo failist ridade kaupa lugemise kohta,
// mis lihtsalt kopeerib faili.
//
// NB! Vt teisi naiteid Ecki opik sektsioon 10.3
//
// Olulist tahele panna:
//   - Programm loeb kasurealt sisendfaili ja valjundfaili nimed
//   - Valjundfaili kirjutatakse read, tapselt nagu sisendist loetud
//   - Kui valjundfail oli varem juba olemas, siis programm ei tee koopiat ja peatub.
//   - Rea kaupa lugemiseks kasutab BufferedReader klassist funktsiooni readLine
//   - Trykkimiseks kasutatav println on sama, mis System.out jaoks println, ainult
//     et valjund laheb avatud faili, mis on System.out asemel.
//   - Avatud failid tuleb peale nende kasutamist sulgeda


// Must import java.io.* in order to get access to libraries

import java.io.*;

public class ioproov {

  public static void main(String[] args) {
    
    String sourceName;
    String copyName;
    
    /* Get two file names from the command line.
       If the command line does not have a legal form,
       print an error message and end this program. */
    
    if (args.length == 2) {
      sourceName = args[0];
      copyName = args[1];      
    }
    else {
      System.out.println("Usage:  java ioproov <source-file> <copy-name>");      
      return;
    }
    
    
    /* If the output file already exists,
       print an error message and end the program. */
      
    File file = new File(copyName);
    if (file.exists()) {
      System.out.println("Output file exists. Exiting.");
      return;  
    }
    
    // All file I/O operations must be done within a try/catch statement
    
    try {

      // Set up the proper readers and writers
      FileReader file_reader = new FileReader(sourceName);
      FileWriter file_writer = new FileWriter(copyName);
      BufferedReader br_reader = new BufferedReader(file_reader);
      PrintWriter pr_writer = new PrintWriter(file_writer);

      // Get the first line of the file
      String line = br_reader.readLine(); 
     
      // check to see if it is null - end of file
      while (line != null) {

        // print line to output file
        pr_writer.println(line);

        // get next line of input file
        line = br_reader.readLine();

      } // while loop
      
      // Finally you must close input and output streams!
      
      file_reader.close();
      file_writer.close();
      
    } //try

    // catch any exceptions thrown
    catch (IOException e) {
      //print error and exit program
      System.out.println(e);
      System.exit(1);
    }
  }
}