Difference between revisions of "CISC181 S2017 Lab1"

Revision as of 11:51, 13 February 2017

• 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
  • If you haven't already, paste the following into MyClass: public static void main(String[] args) { System.out.println("Hello, world!"); }
  • Confirm that you can build and run it (by pressing the green triangle button or choosing "Run" from the Run menu)
• Modify MyClass.java as follows:
• Besides the main method, create two other methods in Lab2: static void heronsFormula() { ... } and static void convertSeconds() { ... } (explained in the subsections below)
• Your main() should initially contain 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 a Scanner to read it
  • If a valid choice is made, call that function immediately. Otherwise print and error message
  • Let the program end (no loop -- just print, read, execute one time)

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

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 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 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.

Use proper naming and formatting style throughout your code.

Submit your MyClass.java on Sakai by Friday, February 17