CISC181 S2017 Lab1

• Download Android Studio and install it on your machine
• Either on your machine or on an eCalc machine in lab:
  • Make a new project following these instructions
  • Confirm that you can build and run it (by pressing the green triangle button or choosing "Run" from the Run menu)
  • As explained in the subsections below, modify static void main() and create two other methods in Lab2: static void heronsFormula() { ... } and static void convertSeconds() { ... }
• Submit your MyClass.java on Sakai by Friday, February 17

Use proper naming and formatting style throughout your code.

static void main()

Your main() should do the following:

• Tell the user (using println()) that they can choose either of the two functions above
• Prompt the user to enter a number to choose one of the options (1 for Heron's, 2 for convert seconds) and use the Scanner class to read it
• If a valid choice is made, call the corresponding function immediately. Otherwise print an error message
• Let the program end (no loop -- just print prompt, read response, and execute one time)

static void heronsFormula()

You will compute several geometric identities involving a general triangle with sidelengths a, b, and c as shown below.

Your function should:

• Declare these sidelength variables as double, prompt the user to enter them, and read each in using the Scanner class.
• Heron's Formula gives a method to compute the area A of the triangle (ignore the fact that A is also the name of one of the triangle vertices). Follow the link and use the first formula to:
  • Derive the semi-perimeter s and area A from a, b, and c using Java math expressions and/or functions
  • Report both s and A with System.out.println().
• The Law of Cosines can be used to calculate the angle γ (gamma) between a and b (second formula in Applications section of link). Math.acos() will give the angle in radians; please convert it to degrees and report it with System.out.println()
• You might notice a lot of decimal places printed in your answers. Change your println() to format as necessary to only print 2 digits after the decimal for s, A, and γ.

static void convertSeconds()

This method should ask the user to enter an integer which represents a length of time t in seconds, and then compute and print out the number of d days, h hours, m minutes, and s seconds corresponding to t on separate lines.

When you are satisfied that you can calculate d, h, m, and s correctly, use branching to modify your printing so that (1) you start with the first non-zero time unit (i.e. do not print leading zero values), and (2) you print "1 day" instead of "1 days", "1 hour" instead of "1 hours", etc. where appropriate (i.e., do not use plural for a value of 1). Some example outputs are below:

If the user inputs "67", the output should be

1 minute
7 seconds

and if they input "8880" the output should be

2 hours
28 minutes
0 seconds

For this function you may assume that t is positive, and you do not have to use a long