EXCEPTION HANDLING AND TEXT I/O - Introduction to Java Programming: Comprehensive Version - page 483

4 catch (MalformedURLException ex) {
5 ex.printStackTrace();
6 }

A MalformedURLException is thrown if the URL string has a syntax error. For example,
the URL string “ http:www.google.com/index.html ” would cause a MalformedURLException
runtime error because two slashes ( // ) are required after the colon ( : ). Note that the http://
prefix is required for the URL class to recognize a valid URL. It would be wrong if you replace
line 2 with the following code:

URL url = new URL( "www.google.com/index.html" );

After a URL object is created, you can use the openStream() method defined in the URL class
to open an input stream and use this stream to create a Scanner object as follows:

Scanner input = new Scanner(url.openStream());

Now you can read the data from the input stream just like from a local file. The example in
Listing 12.17 prompts the user to enter a URL and displays the size of the file.

L ISTING 12.17

ReadFileFromURL.java
1 import java.util.Scanner;
2
3 public class ReadFileFromURL {
4 public static void main(String[] args) {
5 System.out.print( "Enter a URL: " );
6 String URLString = new Scanner(System.in).next();

enter a URL

7
8 try {
9 java.net.URL url = new java.net.URL(URLString);
10 int count = 0 ;
11 Scanner input = new Scanner(url.openStream());
12 while (input.hasNext()) {
13 String line = input.nextLine();
14 count += line.length();
15 }
16
17 System.out.println( "The file size is " + count + " characters" );
18 }
19 catch (java.net.MalformedURLException ex) {
20 System.out.println( "Invalid URL" );
21 }
22 catch (java.io.IOException ex) {
23 System.out.println( "I/O Errors: no such file" );
24 }
25 }
26 }

create a URL object

create a Scanner object
more to read?
read a line

MalformedURLException

IOException

Enter a URL: http://cs.armstrong.edu/liang/data/Lincoln.txt
The file size is 1469 characters

Enter a URL: http://www.yahoo.com
The file size is 190006 characters