Lab 2.1 — A Floating Point Averager (ExamGrader)

• The exams should still be integers.

Lab 2.2 — A Weighted Averager (WeightedAverager)

Write a program that prompts the user for a project, midterm and final and displays their weighted average (as a floating point, i.e., double) according to the following table:

Project	20%
Midterm	30%
Final	50%

(Notice this is very similar yo the previous lab, but with weighted averages, and the prompts and output are different … but it still makes sense to copy Lab 2.1 for your starting point. Starting from a similar program is often simpler than starting from scratch and a useful skill to master.)

Sample Test Run

Here is a sample execution of the program.
User input is in bold. Your program should replicate the prompts and output:

Lab 2.3 — Revisiting Weighted Averages (WeightedAverager) Approval

Modify Lab 2.2 so that the user is prompted for the weights of the exams (see sample run).

Sample Test Run

Here is a sample execution of the program.
User input is in bold. Your program should replicate the prompts and output:

Lab 2.4 — Extracting the Integer and franctional Portions of a Floating Point Value (Casting) Approval

Floating point values — double (and float) have two parts to them: the integer portion and the fractional portion. For example, 15.25 has an integer portion of 15 and a fractional portion of 25.

You are to write an app that prompts the user for how many values to process; reads in that many doubles, and prints it out together with its integer and fractional portions. When you are done, print out the number of values processed.

Sample Test Run How many doubles? 5 Enter a double: 3.5 double: 3.5 integer portion: 3 decimal portion: 0.5 Enter a double: 7.0 double: 7.0 integer portion: 7 decimal portion: 0.0 Enter a double: 10.25 double: 10.25 integer portion: 10 decimal portion: 0.25 Enter a double: 0.234 double: 0.234 integer portion: 0 decimal portion: 0.234 Enter a double: 6.0 double: 6.0 integer portion: 6 decimal portion: 0.0 5 numbers processed

Implementing Your App

• The way to get the integer portion of the double is to chop off the fractional portion … we can do that by converting the double to an integer
  • We learned about the (double) (conversion operator) in class; it converts an int value into a double. The (int casting operator does the reverse: it converts a double into and int. e
    • We used the double cast in case to force floating point division. However, we don't need it for assigning an integer to a double; i.e.,

      double d = 15;
      						

      or

      int i = 15;
      double d = i;
      						

      are perfectly legal since no information is lost.
    • However, going in the opposite direction; i.e.;

      int i = 15.6;
      						

      is illegal because of the possible (and in this example definite) loss of information.
      • Thus if we need to perform the conversion (as we do in our app as we will explain), we need to use the int cast:

        double d = 15.6;
        int i = (int)d;
        								

        and similarly when assigning a double to an int.
• Once we have the integer portion, we can subtract it from the double; we then end up with the fractional portion
  • Remember, arithmetic performed with integer and doubles is called mixed arithmetic, is legal, and evaluate to a double result.