Difference between revisions of "CISC181 F2017 Lab0"

Revision as of 13:28, 4 September 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
  • Confirm that you can build and run it (by pressing the green triangle button or choosing "Run" from the Run menu)
  • Add your name and section number in a comment before the class declaration
  • As explained in the subsections below, modify static void main() and create two other methods: static void heronsFormula() { ... } and static void convertSeconds() { ... }
• Submit your MyClass.java on Sakai by Monday, September 11

Use proper naming and formatting style throughout your code.

static void main(String[] args)

Your main() should do the following:

• Tell the user (using println()) that they can choose either of the two functions above by entering a single number: 1 for Heron's, 2 for convert seconds
• Use the Scanner class to read that number. Check that it really is either 1 or 2
• 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 on a single line, separated by spaces, 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.
• To summarize: take in 3 space-separated numbers on a single line, do calculations, and print out 3 numbers on their own lines with nothing else. If illegal values are given (negative sidelengths, or three sidelengths that cannot possibly form a triangle), then print out a one-line error message without doing any calculations.

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 you:

• Start with the first non-zero time unit (i.e. do not print leading zero values)
• 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