Description
Internet browsers provide users with a lot of flexibility in navigating sites and documents on the Internet. As we all
know, users can load individual web pages, return to previously viewed pages, move forward to more recently viewed
pages, and display a history of visited pages. Your task is to write a Java class to simulate the navigational tools of an
Internet browser, using Stack object(s) to keep track of the sites visited.
Your assignment is to implement the Browser class, with the methods described below. A Browser object contains a
web document represented by its Uniform Resource Locator or URL:
• A no-argument constructor that simply initializes a Browser object with url “http://www.ulm.edu”
• A constructor that takes an argument a String object representing a page to be loaded initially. If successful (see
load method below), the argument string should become the URL for the current page. Otherwise, the Browser
object should be initialized with the page “ERROR: CANNOT FIND ”
• boolean load(String url): attempts to load the web page with the URL passed as argument. To determine
whether the URL is valid, use the java URL class from the java.net package (see example below). If
successful, the URL argument should become the current page and the method should return true. Otherwise,
the method should return false and the current page should be “ERROR: CANNOT FIND ” (Note that
loading a page erases any “forward” pages)
• String currentPage(): returns a String object containing the URL for the current page.
• boolean canGoBack(): returns true if there is a previous page in the browsing history, false otherwise.
• boolean canGoForward(): returns true if there is a next page in the browsing history, false otherwise.
• String goBack(): loads and returns the previous page in the browsing history. If there is no “previous”
page to load, the method should have no effect and should simply return the current page.
• String goForward(): which should “load” and return the next page in the browsing history. If there is no
“next” page to load, the method should have no effect and should simply return the current page.
• String history(): returns a list of the pages loaded in the current browsing session, with most recent
page listed first. No “ERROR: CANNOT FIND url” pages should be included in the history.
REQUIREMENTS and RESOURCES:
▪ Download and use the StackInt interface and the LinkedStack class studied in class. Do not modify
either one. Be sure to declare any Stack variables using the StackInt type.
▪ The Java URL class can be used to establish a connection to a resource on the internet. In the simplest case, the
constructor accepts a String containing a URL. The resulting object can be used to open a stream, read its
contents, etc. The getContent() method can be used to test whether the URL corresponds to an actual
website. The constructor throws an exception if the URL is not properly formatted. Sample code segment:
try {
URL webpage = new URL(url);
if (webpage.getContent() != null)
… // url properly formatted and found
}
catch (Exception e) { // url was not properly formatted
…
}
▪ The BrowserTest class is provided for basic testing. Once you are satisfied you class works as expected,
submit Browser.java to Mimir for testing.
