CS205 Notes 5 (1 September 2006)

cs205 Friday 1 September 2006

• Monday, 4 September: remaining reading for ps2: Chapter 4, Chapter 10 through 10.2, and Chapter 5 through section 5.2
• Friday, 8 September: Problem Set 2

Validation

How can we increase our confidence that a program works as intended?

For what kinds of programs is exhaustive testing possible?

What is a successful test case?

What is the difference between testing and analysis?

What are the advantages and disadvantages of spending time on analysis instead of testing?

Scanning

package wordcount;
import java.io.*;
import java.util.Scanner;

public class WordCount {
   public static void main(String[] args) {
      int linecount = 0;
      int wordcount = 0;
      int lencount = 0;

      if (args.length < 1) {
         System.err.println("Usage: first parameter must name a file.");
         System.exit(0);
      }

      // Java compiler complains about non-initialization without this.
      Scanner s = null; 

      try {
         s = new Scanner(new File(args[0]));
      } catch (FileNotFoundException e) {
         System.err.println("Unable to open file: " + e);
         System.exit(0);
      }

      while (s.hasNextLine()) {
         String line = s.nextLine();
         linecount++;
         Scanner linescanner = new Scanner (line);
         while (linescanner.hasNext()) {
            String word = linescanner.next();
            wordcount++;
            lencount += word.length();
         }
      }
    
      System.out.println ("Lines: " + linecount + " Words: " + wordcount 
         + " Characters in words: " + lencount);
   }
}