Homework IV Answers

Part I

1.
java.net.URL

Code fragment:

import java.net.URL;
import java.io.*;
...
  URL url = new URL("url");
  InputStream is = url.openStream();
  InputStreamReader isr = new InputStreamReader(is);
  BufferedReader br = new BufferedReader(isr);

You can now read from the stream using the BufferedReader br.

2.
java.util.HashSet is probably the most suitable class. Other classes you could
use are (all from the java.util package): Vector, LinkedList, Hashtable.

3.
java.io.BufferedReader or java.io.LineNumberReader

Code fragment:

import java.io.*;
...
  FileReader fr = new FileReader("file name");
  BufferedReader br = new BufferedReader(fr);
  String line
  ...
  line = br.readLine();


Part II

1.
public class AddNumbers {
  public static void main(String args[]) {
    int sum = 0;
    for (int i = 0; i < args.length; i++)
      try {
        sum += Integer.parseInt(args[i]);
      }

      catch (NumberFormatException e) {
        System.out.println("Bad number: " + args[i]);
        System.exit(1);
      }

    System.out.println(sum);
  }
}