CISC181 F2017 Lab1

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  • Make a new project (but now n = 1) following these instructions
  • Name your class "Lab1". This happens when you are creating a new module, in the Java class name field
    • 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 the three other methods described below.
  • Submit your on Sakai by Monday, September 18

static void main(String[] args)

Your main() should do the following:

  • As with Lab #0 last week, give your user the choice of several options (using println() or printf()), to be chosen by inputting a single number (which is read with a Scanner object). This time, the options are: 1 to solve a basic physics problem, 2 to draw a particular pattern with print commands, and 3 to find the most common character in a string. Whichever choice is given (after error-checking), take the steps specified below and call the corresponding function.
  • Option 1: Ask the user to enter theta and v, read them, pass them to computeDistanceToLanding(), and print the returned result.
  • Option 2: Ask the user to enter two chars and a positive number. Read these and pass them to drawLayeredPyramid().
  • Option 3: Ask the user to input a string on its own line. Read this and pass it to mostCommonChar(). Print the returned value.
  • For all user inputs, check for legality here in main(). If there is a problem, print an informative message with the word "error" somewhere in it, and let the program end.

static float computeDistanceToLanding(float thetaDegrees, float initialVelocityMetersPerSecond)


Suppose you want to calculate how far away a cannonball will land on Earth if fired at an inclination angle of theta degrees and an initial velocity of v meters / second. Assume that the ground is perfectly planar, the cannon is at a height of 0, and neglect drag from atmospheric resistance. I am not going to provide the relevant physics formula -- finding it and turning it into Java is your assignment here. Once you have calculated the distance, return the answer in meters.

static void drawLayeredPyramid(int numLayers, char firstChar, char secondChar)

Consider the following pattern:


It consists of 10 alternating rows of $ and ¢ characters. The first row has 10 columns of characters, and each successive row has one less. drawLayeredPyramid() should make a similar pattern with numLayers rows, alternating characters firstChar and secondChar. This will require at least one loop; see the slides for the Sep. 13 lecture for material about doing loops in Java.

static char mostCommonChar(String queryString)

Iterate (aka loop) through the characters in queryString and count how many times each character occurs. Whichever character occurs the most times, return it. Ties should be broken in alphabetical order--that is, if 'a' occurs 7 times and 'b' occurs 7 times, return 'a'. To make a comparison, use

This is somewhat tricky, but you can (and must, for this assignment) do this without any external data structures such as arrays. The only String functions that you can use here are charAt() and length().