PrintWriter  fileApnd = new PrintWriter(new  FileWriter(filename, true);

• program that obtain certain type of resources such as memory and file must return those resources to the system
• typical use of finally block is to close any files opened in the try block
• the code in the finally block will be executed whether or not the corresponding try-block throws an exception, and regardless of whether or not any thrown exception there is caught by any of the corresponding catch-blocks

import  java.io.*;
public class ReadClient  {

    private static BufferedReader  stdIn = new
	BufferedReader(new  InputStreamReader(System.in));

    public static void  main(String[]  args) throws	IOException  {
        String text;
        int count = 0;
        BufferedReader fileIn;

        do  {
               try  {
                      System.out.println("Enter file name:");
                      fileIn  =  new BufferedReader(new FileReader(stdIn.readLine()));
                      break;
               } catch (FileNotFoundException  fnfe)  {
                            System.out.println(fnfe.toString());
               }
        }  while (true);

        while ( ( text = fileIn.readLine() ) != null ) {
                 System.out.println(++count + " " +  text);
        }

        fileIn.close();
    }
}

• break string into token
• "Fred Chan_213 Yuen Long Avenue_D_41.03" represent a client record of name, address, transactionCode, and transactionAmount
• '_' and space can be used as delimiter
• StringTokenizerClassDemo
• class ReadClientToken

  import  java.io.*;
  import  java.util.*;
  
  public class ReadClientToken {
  
      private static BufferedReader  stdIn = new
  	BufferedReader(new  InputStreamReader(System.in));
  
      public static void  main(String[]  args) throws	IOException  {
          String text;
          int count = 0;
          BufferedReader fileIn;
  
          do  {
                 try  {
  	    System.out.println("Enter file name:");
                        fileIn  =  new BufferedReader(new FileReader(stdIn.readLine()));
                        break;
                 } catch (FileNotFoundException  fnfe)  {
                              System.out.println(fnfe.toString());
                 }
          }  while (true);
  
          while ( ( text = fileIn.readLine() ) != null ) {
                   StringTokenizer  st = new  StringTokenizer(text, "_");
                   String clientName = st.nextToken();
                   String clientAddress= st.nextToken();
                   String trxCode= st.nextToken();
                   double trxAmount= Double.parseDouble(st.nextToken());
  
                   System.out.println(++count + " " +
                                                clientName + " " +
                                                clientAddress + " " +
                                                trxCode + " " +
                                                trxAmount);
          }
  
          fileIn.close();
      }
  }