• pass with a grade in the C range
• get a B of some sort
• or get full or nearly full credit (A or A-)

Recall books have been assigned as reading and/or specified as references in Books24x7 (or Horstmann, from IU Bookstore).

Knowledge of parts 1, 2, 3, 4 is necessary to pass with a grade in the C range.

Add to that knowledge of part 5 plus at least a third of the homework turned in and you could get a grade in the B range.

Add to that knowledge of part 6 plus at least two thirds of the homework turned in and you could get an A or an A-.

If you have all the homework turned in perfectly you might already be in the A or A- range.

So these are the rules, and these are the available times for individual appointments.

1. You should be able to write a program that prints some text.

   This is the basic edit-compile-run-print loop. Example:

   class One {
     public static void main(String[] args) {
       System.out.print("Boy, th"); 
       System.out.print("is is g"); 
       System.out.println("reat!"); 
     }
   }

2. You should be able to write a program that asks the user for two numbers, reads them and sums them up then prints the sum.

   The example below uses a scanner for user input, variables and simple arithmetic:

   import java.util.*; 
   
   class Two {
     public static void main(String[] args) {
       Scanner s = new Scanner(System.in); 
       System.out.print("First number: ");
       double a = s.nextDouble(); 
       System.out.print("Second number: ");
       double b = s.nextDouble(); 
       System.out.print(a); 
       System.out.print(" + "); 
       System.out.print(b); 
       System.out.print(" = "); 
       System.out.print(a + b); 
       System.out.println();
       System.out.println(a + " + " + b + " = " + (a + b)); 
       String output = a + " + " + b + " = " + (a + b);
       System.out.println(output); 
     } 
   }

   Note we print the result in three different ways.

3. You should be able to write a program that
        a) generates two random integers in the range -50 to 50 (let's call them n and m)
        b) asks the user what the answer is for n + m
        c) reads the answer from the user and
             c.1) if the answer is right says so
             c.2) otherwise says: "no, the right answer was..." and prints the right answer

   This program uses basic if statements to test a condition then take the correct course of action based on the test's result.

   import java.util.*; 
   
   class Three {
     public static void main(String[] args) {
       Scanner s = new Scanner(System.in); 
       int n, m; 
       n = (int)(Math.random() * 100 - 50); 
       m = (int)(Math.random() * 100 - 50); 
       System.out.print("What is " + n + " + " + m + "? Answer: "); 
       int answer = s.nextInt(); 
       if (answer == n + m) {
         System.out.println("That's right! " + n + " + " + m + " = " + answer); 
       } else {
         System.out.println("No, " + n + " + " + m + " = " + (n + m) + ", not " + answer); 
   
       } 
     } 
   }

4. Write a program that asks the user for two numbers:
        a) an initial balance
        b) an interest, yearly
   Then the program keeps adding the interest to the balance counting
   the years until
        a) either 20 years have passed, or
        b) the amount has now doubled

   Here's an example:

   import java.util.*; 
   
   class Four {
     public static void main(String[] args) {
       Scanner s = new Scanner(System.in); 
       System.out.print("Enter amount: "); 
       double initialAmount = s.nextDouble();
       System.out.print("Enter interest rate: "); 
       double rate = s.nextDouble();
       int yearsPassed = 0; 
       double currentAmount = initialAmount; 
       while (yearsPassed < 20 && initialAmount * 2 > currentAmount) {
         double interest = rate * currentAmount / 100; 
         currentAmount = currentAmount + interest;
         yearsPassed += 1; 
       }
       String estimate = "\n(you need to wait longer to double up your money) "; 
       if (currentAmount >= 2 * initialAmount) 
         estimate = "\n(that's twice as much money as you started with) "; 
       System.out.print("In " + yearsPassed + " years your balance"); 
       System.out.println(" will become " + currentAmount + estimate);     
     } 
   }

   This programs uses loops to repeat a block of statements until we obtain the desired outcome.

5. Write a program that reads a number of numbers from a file and prints them in ascending order in another file.

   import java.io.*; 
   import java.util.*; 
   
   class Five {
     public static void main(String[] args) throws FileNotFoundException, IOException {
       Scanner s = new Scanner(new File("numbers.txt")); 
       int length = 0; 
       String numbers = ""; 
       while (s.hasNextInt()) {
         int num = s.nextInt(); 
         numbers += " " + num; 
         length += 1; 
       }
       int[] nums = new int[length]; 
       StringTokenizer t = new StringTokenizer(numbers); 
       for (int i = 0; i < length; i++) 
         nums[i] = Integer.parseInt(t.nextToken()); 
       System.out.println(Arrays.toString(nums)); 
       Arrays.sort(nums); 
       String sorted = Arrays.toString(nums); 
       System.out.println(sorted); 
       String fileName = "numbers-sorted.txt" ;
       FileWriter writer = new FileWriter( fileName );
       for (int i = 0; i < length; i++) 
         writer.write(nums[i] + "\n"); 
       writer.close();
     }
   }

   My test file for this program was numbers.txt shown below (note the format):

   
       1      8
    20     5      16
    5
    1
         20
                 4
   

   You'll have to run the program to see what it produces (output on screen and output in a text file).

6. (We list two problems here, choose one): Problem One, Problem Two

   The solution for Problem One can be given using two-dimensional arrays.

   That aproach has the advantage of being able to build the pattern in more than one pass.

   Here however we present a one-pass solution, that uses no storage, and just prints the pattern:

   import java.util.*; 
   
   class Six {
     public static void main(String[] args) { 
       Scanner s = new Scanner(System.in); 
       System.out.print("What size: "); 
       int size = s.nextInt(); 
       for (int i = 0; i < size; i++) {
         for (int j = 0; j < size; j++) 
           if (i == 0 || i == size-1 || i+j == size-1 || i == size/2 && j>=size/4 && j<= 3*size/4)
             System.out.print("* "); 
           else 
             System.out.print("  "); 
         System.out.println(); 
       } 
     } 
   }

   For the second problem a two dimensional array of integers is indispensable:

   class Magic {
     public static void main(String[] args) {
       int n = Integer.parseInt(args[0]);
       int[][] sq = new int[n][n];
       int i = sq.length - 1;
       int j = sq.length / 2;
       for (int k = 1; k <= n * n; k++) {
         sq[i][j] = k;
         int ni = (i + 1) % sq.length;
         int nj = (j + 1) % sq.length;
         if (   sq[ni][nj] != 0 
            || (i == sq.length - 1 && j == sq.length - 1)) 
         { 
           ni = i - 1;
           if (ni < 0) 
             ni = sq.length;
           nj = j;
         }
         i = ni;
         j = nj;
       }
       for (i = 0; i < sq.length; i++) {
         for (j = 0; j < sq[i].length; j++) {
           String num = "   " + sq[i][j];
           System.out.print(num.substring(num.length() - 3) + " ");
         }
         System.out.println();
       }
     }
   }

   Note that the input (the size) comes from the command line in this case.