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Mission: Hello!

  • Show a string on your computer's screen.
  • Use comments in your code.
  • Use javadoc in your code.
  • Capture & verify your 'standard' output!

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Mission: Your Main 'Params

  • Learn how to read command-line parameters.
  • Discover two ways to iterate through an Array.
  • Review how to index an array using a subscript.

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Mission: Main 'Param Meta

(1) Create a public, static main function to:

  • Detect command-line parameters.
  • Test for a 'null parameter.'
  • Use explicit, as well as implicit void return conventions.

(2) Test the above using JUnit.

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Mission: Static Member Functions

(1) Create a private, static function.

  • Function to combine string parameters together.
  • Input: String[]
  • Output: String

(2) Call the above from within your static main function.

(3) Test that main using JUnit.

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Mission: StringBuilder

(1) Create a private, static function.

  • Function to combine string parameters together.
  • Inputs: String[], StringBuilder
  • Process: Add spaces between strings.
  • Process: Add a newline at the end of the string.
  • Output: void

(2) Create a main

  • Check for valid parameters.
  • Pass command-line parameters to the private function, above.
  • Dsplay the results.

(3) Test using JUnit.

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Mission: StringBuffer & Integral Arrays

(1) Create a private, static function.

  • Function to combine integrals together into an addive 'expression string.' (*)
  • Inputs: int [], StringBuffer
  • Output: void

(2) Create a public, static function.

  • Function to re-use the above.
    • Inputs: int ...
  • Output: String

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Mission: Total null Detections

(1) Create a public, static function.

  • Function to combine Float instances together into an additive 'expression string.'
  • Inputs: Float []
  • Processing: Convert null instance values to 0.
  • Processing: Re-use (2), below.
  • Output: An additive expression string.

(2) Create a public, static function.

  • Function to combine float values together into an additive 'expression string.'
  • Inputs: float []
  • Output: An additive expression string.

(3) Create a JUnit @Test to exercise the above.

  • Prove that instanced types (e.g Float) can be null.

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Mission: Decimal Precisions

The Internet has much to say about floating point accuracies. The net effect (no pun intended) of which easily justifies Java's creation of the BigDecimal class.

Worthy of several activities in its own right, the mission here is merely to demonstrate the basics.

(1) Create public, static functions to add, subtract, multiply, and divide double values.

  • Inputs: BigDecimal result and Double ... vals for each.
  • Processing: Ignore any null input for vals.
  • Processing: Ignore null instance values.
  • Processing: Perform the function-named operation.
  • Output: A final BidDecimal result.

(2) Review the test case to examine BigDecimal's primitive type support.

  • Notice the .valueOf(), .floatValue(), and other .*Value() operations.
  • Notice how to extract fractional as well as whole values.

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Mission: The Scanner Class

If you have been craving more complex activities, then you are in luck!

In this activity we will employ Java's Scanner class to allow us to document & test those floating-point oddities. We will also need to manage some exceptions.

(1) Create public, static functions to convert strings into any possible Integer, Float, Double, or BigDecimal instances. Return null on error.

(2) Test the above conversions using JUnit.

  • Place your scanner's input into a File (optional.)

(3) Create & test a public, static function called addNum.

  • Input: A Scanner.
  • Processing: Aggregate individual int, float, and double totals.
  • Processing: Ignore any other input.
  • Output: Show each individual aggregation.
  • Output: Show the combined values as "SIGMA".

(4) Repeat the above processing to create addBigNum.

  • Input: A Scanner and int precision
  • Processing: As per above, using only Integer and BigDecimal.
  • Output: As above, yet with "SIGMA" rounded to the requested input precision.

(5) Finally, create a public, static main to scan the standard input for any values.

  • Note that System.in will require a CTRL+d / CTRL+z (aka "EOF") to stop the scanning process!

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Mission: RPN Calculator

Now is a good time to demonstrate how to use what we have learned to create a 'Reverse Polish Notation' - or R.P.N - calculator.

Your mission is to create a "White Box" test:

  • Run CalcRPN.Java
  • Review the code
  • Create test cases

NOTE: If the term "White Box Testing" is new to you, then you might also enjoy Testing Success?

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Mission: Getting Classy

Creating class instances is a fine way to help us manage more than any single, static, set of information. Reviewing the new CalcJob class therefore, notice that managing those "nasty nulls" is just one of the many benefits?

Users might also want their calculators to be working on several calculation jobs at once...

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Mission: Nested Classes

Nesting one class within another need not be so uncommon!

In this case, when our evolvng Nexus exclusively requires the CalcJob instance, it is often a good time to nest things together.

TODO: Work in progress!

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Mission: Static Class Nestings

Nesting one class within another need not be so uncommon!

In this case, when our evolvng Nexus exclusively requires the CalcJob instance, it is often a good time to nest things together.

TODO: Work in progress!

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