Building Java Programs

Lab: Parameters

 

 

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 2: Parameter Mystery

Exercise 3: Parameter Mystery

Exercise 4: Parameter Mystery

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 6: printGrid 

Exercise 7: printSquare