CS62 - Spring 2021 - Lab 2

Example code in this lecture

   CardDealer

Lecture notes

  • What does the constructor do in CardDealer in CardDealer code
       - What does the constructor do?
          - creates a new array for number of decks * 13 * 4 entries
          - adds each card for each deck to the array
             - outer loop is over the number of decks
             - second loop is over suits
             - third loop is over numbers      

  • initializing arrays
       - often, we'll initialize an array and then fill it in, e.g.,
          int[] x = new int[10];

          x[0] = 2;
          ...

       - sometimes (e.g., with constants), we'll want to initialize the array with values. To do this, use curly braces
          int[] x = {1, 2, 3, 4, 5};

  • Look at the CardDealer in CardDealer code
       - What does the shuffle method do?
          - for each card, pick another random entry and swap the entries

       - Where does Random come from?
          - it's another class that we imported!

  • A package is a collection of classes
       - usually they're related
       - Any class inside a particular package may use any other class in the package without doing anything special
       - If you want to use a class that is not inside your package, you need to import it
       - To import a class:
          import <package_name>.<class_name>
          
          - sometimes, there are nested packages, e.g.

             import <outer_package>.<inner_package>.<class_name>

          - For example:
             import java.util.Random

             - imports the Random class from the java.util package
             
             import java.util.Scanner

             - imports the Scanner class from the java.util package

       - To write your own package:
          - Packages are indicated in two ways (both are required):
             1) All classes inside a packages should be in a directory with the packages name
             2) All classes inside a package should start with package <package_name>;

  • Look at the CardDealer in CardDealer code
       - What does the printDeck method do?
          - it's static, so it doesn't have access to the instance variables
          - creates a new card dealer and then prints out the entire deck
          - utilizes next and getNext
             - both use position to keep track of where we are
             - using this pair of methods is a common way to iterate through data. we'll see it a lot!

  • Look at the CardPrinter class in CardDealer code
    •