Sams Teach Yourself Java™ in 24 Hours (Covering Java 7 and Android)

ptg7068951

260 HOUR 18:Handling Errors in a Program

LISTING 18.5 The Full Text of PageCatalog.java

1: importjava.net.*;

2:

3: public classPageCatalog {

4: public static voidmain(String[] arguments) {

5: HomePage[] catalog = new HomePage[5];

6: try {

7: catalog[0] = new HomePage(“Mark Evanier”,

8: “http://www.newsfromme.com”, “comic books”);

9: catalog[1] = new HomePage(“Todd Smith”,

10: “http://www.sharkbitten.com”, “music”);

11: catalog[2] = new HomePage(“Rogers Cadenhead”,

12: “http://workbench.cadenhead.org”, “programming”);

13: catalog[3] = new HomePage(“Juan Cole”,

14: “http://www.juancole.com”, “politics”);

15: catalog[4] = new HomePage(“Rafe Colburn”,

16: “www.rc3.org”);

17: for (int i = 0; i < catalog.length; i++) {

18: System.out.println(catalog[i].owner+ “: “ +

19: catalog[i].address+ “ — “ +

20: catalog[i].category);

21: }

22: } catch(MalformedURLException e) {

23: System.out.println(“Error: “+ e.getMessage());

24: }

25: }

26: }

When you run the compiled application, the following output is displayed:

Output▼

Error: no protocol: http://www.rc3.org

The PageCatalogapplication creates an array of HomePageobjects and then

displays the contents of the array. Each HomePageobject is created using up

to three arguments:

. The name of the page’s owner
. The address of the page (as a String, not a URL)
. The category of the page

The third argument is optional, and it is not used in Lines 15–16.

The constructor methods of the HomePageclass throw

MalformedURLExceptionerrors when they receive a string that cannot be

converted into a valid URLobject. These exceptions are handled in the

PageCatalogapplication by using a try-catchblock.