Chapter 6
Section 10
"Random Number Generation"

- generate random numbers using the random method of the Math class
- random method
  - pseudorandom number generator
    - not truly random
    - eventually the numbers returned will repeat
  - returns a double >= 0.0 and < 1.0
- generally want integers
- conversion so that number generated will fall in desired range [min, max]
  - Y = floor(X * (max - min + 1) ) + min
    - special case for min = 1: Y = floor( x * max ) + 1
  - code version: int randomNumber = (int) (Math.floor(Math.random() * (max-min+1)) + min);
- timing execution
  - use the Date class to grab the start time and end time
    - Date startTime = new Date();
  - put the difference in a long to get elapsed time in milliseconds
    - long elapsedTime = endTime.getTime() - startTime.getTime();
  - rough estimate because varies with the CPU that it is run on
  - if difference is 0, means that it was so fast we couldn't measure it, not that it took no time
- break statement
  - can be used in things other than switch; e.g., if statement or a loop to immediately stop execution
- exit a program using System.exit(0);

Quick Check
1.  int randomNumber = Math.floor( Math.random() * (50 - 20 + 1) ) + 20;
2.  about 5250 s