Week 8: exam review

Exam 1 (on Wednesday, March 6) will cover all the review material, plus design and implementation of classes and interfaces. This corresponds roughly to book chapters 1-7, plus parts of 8.

Example problems

1. Add an equals method to the class below that represents a fraction. The method should return true if the two fractions represent the same number.

   
   public class Fraction {
       // Represent the number n/d.
       public final int n; // numerator
       public final int d; // denominator
       public Fraction(int n, int d) {
           this.n = n;
           this.d = d;
       }
   }
       

2. What does the following code print?

   
   int x = 5;
   for (int i = 0; i < 5; i++) {
       x  = x + i;
       if (x % 2 == 0) {
           System.out.println(x);
       }
   }
       

3. Write a program that reads user input until the user enters a blank line, and the prints the longest line entered.
4. Consider the Callable inteface defined below:

   
   public interface Callable {
       public int call();
   }
       

   Implement this interface in a class called Inc so that the output of the following program is the numbers 1 through 10:

   
   Callable f = new Inc();
   for (int = 0; i < 10; i++) {
       System.out.println(f.call());
   }
       

5. Define a class that has a method called randomString that takes a non-negative integer as input and returns a String made up of random letters in the range a-z.

   The standard library Random class could be helpful. Another useful fact: in Java, computing (char)('a' + 1) results in 'b'.