Solutions for the `Introducing Iteration' exercises

The answers given for exercies 1-5 are examples only. Any program that a) uses a for loop and b) produces the correct output is correct.

1. 1  class Ex31 {
   2  
   3    // Model answer to Exercise 3.1
   4    public static void main(String[] args) {
   5      for (int i = -10; i < 9; i = i + 3) {
   6        System.out.println(i);
   7      }
   8    }
   9  }
   	

2. 1  class Ex32 {
   2  
   3    // Model answer to Exercise 3.2
   4    public static void main(String[] args) {
   5      for (int i = 1; i < 8; i = i + 1) {
   6        System.out.println(i * 3);
   7      }
   8    }
   9  }
   	

3. 1  class Ex33 {
   2  
   3    // Model answer to Exercise 3.3
   4    public static void main(String[] args) {
   5      for (int i = 128; i > 0; i = i / 2) {
   6        System.out.println(i);
   7      }
   8    }
   9  }
   	

4. 1  class Ex34 {
   2  
   3    // Model answer to Exercise 3.4
   4    public static void main(String[] args) {
   5      for (int i = 1, j = 0, k = 0; i < 22; k = i, i = i + j, j = k) {
   6        System.out.println(i);
   7      }
   8    }
   9  }
   	

5. 1  import java.io.*;
   2
   3  class Ex35 {
   4  
   5    // Model answer to Exercuse 3.5
   6    public static void main(String[] args) throws IOException, NumberFormatException {
   7      int x;
   8      String num;
   9      BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
   10 
   11     System.out.print("Please enter an integer: ");
   12     num = in.readLine();
   13     x = Integer.parseInt(num);
   14 
   15     for (int i = 0; i <= 2 * x; i = i + 1) {
   16       System.out.println(i);
   17     }
   18   }
   19 }
   	

6. These are the only correct answers:
   1. 16
   2. 17
   3. 7
   4. 28
   5. 6
   6. 51