CSC 171
Homework 2

Assigned Feb 1, due Feb 11

This looks like a lot of methods to write, but each one is pretty short and simple. They'll probably each be ten to twenty lines long, and most of this is contracts, examples, and inventories.

Programming

For all the programming assignments, be sure to follow the design recipe. First, create a class; for now, all your methods will be in one class. Then, for each method,

1. Write the method contract (either in plain English or in javadoc form) in Java comments.
2. Write examples (either in comments ahead of the method, or in JUnit or Tester form once we get to this).
3. Write the method skeleton.
4. Add an inventory (in comments) between the curly-braces of the method skeleton.
5. Fill in the method body after the commented inventory.
6. Test your method: if you wrote your examples using JUnit, you can just hit the "Run Test Cases" button. If you wrote them using Tester, you can right-click on the test class and choose "testEverything()". If you wrote your examples in comments, copy and paste each example, one by one, into the CodePad, and see whether the answers match what you said they would be.

Be sure to choose meaningful names for methods and parameters, and watch for opportunities to re-use methods you, I, or the textbook have already written.

Also turn in a log of how many errors of different kinds you encountered in the assignment, with brief comments describing each one ("mismatched parentheses" is self-explanatory, but more complex errors might need more description). You may do this using the PSP forms, or simply by keeping track in a text file or on paper and turning it in.

Methods to write

For now, I recommend putting all of these in one class (say, Homework2).

• Develop a method named hoursToMinutes which takes in a number of hours and returns the number of minutes in that many hours.

• Develop a method named daysToHours which takes in a number of days and returns the number of hours in that many days.

• Develop a method named daysToMinutes which takes in a number of days and returns the number of minutes in that many days.
  Hint: re-use previously-written methods. You should be able to write this method with no numbers or arithmetic operators in the method body (although you'll need numbers in your examples, of course).

• Develop a method named squarePerim which takes in the length of a side of a square, and returns its perimeter.

• Develop a method named circleArea which takes in the radius of a circle and returns its area. The formula is π r²; use Math.PI as the value of π.

• Develop a method named avgThree which takes in three numbers (not necessarily integers) and returns their average (i.e. add them up and divide by 3).

• Develop a method named dhmToMinutes that takes in three numbers: how many days, how many hours, and how many minutes, in that order, and returns the total number of minutes.
  Hint: You should be able to write this with no numbers or arithmetic operators in the body of the method, by re-using previously-written methods.

• Develop a method named celsiusToKelvin that takes in a number of degrees Celsius and returns the same temperature as written in Kelvin. (A degree Kelvin is the same size as a degree Celsius, but 0 Kelvin is approximately -273 Celsius. This gives you at least one example: MyClass.celsiusToKelvin(-273) should be about 0.
  Come up with at least two more examples of your own.) Note that the method should handle fractional degrees, not only integers.

• Develop a method named fahrenheitToCelsius that takes in a number of degrees Fahrenheit and returns the same temperature as written in Celsius. (The formula is C = (F-32)*5/9 .)

• Develop a method named fahrenheitToKelvin that takes in a number of degrees Fahrenheit and returns the same temperature in Kelvin.
  Hint: You should be able to write this with no numbers or arithmetic operators in the body of the method, by re-using previously-written methods.

• You've just learned that 0 Kelvin is not -273 C, but more accurately -273.15 C. How much of the previous three methods do you have to change in order to improve the accuracy?

• Develop a method named convert3digits that takes in the "hundreds", "tens", and "ones" digits of a number, in that order, and returns the number. For example, MyClass.convert3digits(5,2,8) should be 528

• Develop a method named convert3reversed that takes in the "ones", "tens", and "hundreds" digits of a number, in that order, and returns the number. For example, MyClass.convert3reversed(7,0,1) should be 107.
  Hint: You should be able to do this with no numbers or arithmetic operators in the body of the method, by re-using previously-defined methods.

• Develop a method named quadraticFormula that takes in the coefficients a, b, and c of a quadratic, and computes the value of the largest real root. You may assume that there is at least one real root. The formula is (-b+sqrt(b²-4ac))/(2a).

Grading standards

Programming:

General skills:

Total:         /450