Building Java Programs

Lab: Parameters

Except where otherwise noted, the contents of this document are Copyright 2019 Stuart Reges and Marty Stepp.

lab document created by Marty Stepp, Stuart Reges and Whitaker Brand

Lab goals

Goals for this problem set:

Parameters

A parameter allows you to pass in a value to a method as you call it.

public static void name(type name) {   // declare
methodName(expression);                // call

Example:

public static void squared(int num) {
    System.out.println(num + " times " + num + " is " + (num * num));
}
...
squared(3);          // 3 times 3 is 9
squared(8);          // 8 times 8 is 64

Exercise : Parameters output

Solving "Parameter Mystery" problems

Exercise : Parameter Mystery practice-it

Exercise : Parameter Mystery practice-it

Exercise : Parameter Mystery practice-it

Exercise : Syntax errors

Exercise - answer

  1. line 5: cannot use variable y without declaring and initializing it
  2. line 5: cannot declare the type of y in the method call
  3. line 6: cannot call printer without the correct number of parameters (2, in this case)
  4. line 7: cannot call printer by passing the correct type of parameters (double, in this case)
  5. line 8: cannot refer to the variable z: it is in scope inside printer, not main
  6. line 11: must provide a type for x
  7. line 11: must provide a variable name for the second parameter
  8. line 12: must refer to the parameters using the exact same spelling
  9. line 13: cannot refer to variables in main that were not passed into printer as a parameter

Exercise - Corrected version

Exercise : printGrid practice-it

Exercise : printSquare practice-it