LAB 37 – Creating and Modifying Text (part 2)

Lab Exercises

Topics

n To manipulate structured text, such as a delimited string.

n To manipulate strings

n To use the swing class JOptionPane

Exercises

12.2 Strings: Character Sequences

i) Create a textfile urls.txt with the following content:

www.google.com

java.sun.com/j2se/1.5

www.linux.org/info/gnu.html

duke.csc.villanova.edu/lewis/

www.csc.villanova.edu/academics/index.jsp

ii) Open a new file in Dr. Java and type in the following program:

//********************************************************************

//  URLDissector.java       Author: Lewis/Loftus

//

//  Demonstrates the use of Scanner to read file input and parse it

//  using alternative delimiters.

//********************************************************************

import java.util.Scanner;

import java.io.*;

public class URLDissector

{

   //-----------------------------------------------------------------

   //  Reads urls from a file and prints their path components.

   //-----------------------------------------------------------------

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

   {

      String url;

      Scanner fileScan, urlScan;

      fileScan = new Scanner (new File("urls.txt"));

      // Read and process each line of the file

      while (fileScan.hasNext())

      {

         url = fileScan.nextLine();

         System.out.println ("URL: " + url);

         urlScan = new Scanner (url);

         urlScan.useDelimiter("/");

         //  Print each part of the url

         while (urlScan.hasNext())

            System.out.println ("   " + urlScan.next());

         System.out.println();

      }

   }

}

ii) Run your program and examine the results.

iii) Remove the throws IOException and rerun the program

iv) Modify the main method by

a. Adding a try { before the file is instantiated, and

}      catch (FileNotFoundException ex)

      {

        System.out.println("File urls.txt not found");

      } 

after the while loop.

i. Change the file name urls.txt to something else and test your program

b. Add         int test = fileScan.nextInt();  inside the while loop and run your program.

c. Add another catch

     catch (Exception ex)

      {

        System.out.println ("Error during read");

      }

            To the end of the try-catch.

d. test your program.

QUESTIONS:

Submit the URLDissector.java files through the DropBox in WebCT.