CS 141 Topics

CS141: Topics for Week 10: Oct 26, 28 & 30, 2015

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Lab

Lab 8: Arrays
Remember to review questions starting on p. 535.

Chapter 7 Arrays and the ArrayList Class: Vocabulary

array (1D, 2D, multi-dimensional)
Declaring an array
Accessing array elements
Initializing an array
Enhanced for-loop
Out of bounds problems
Calculating with arrays:
  ... comparing, summing, min/max, averages, swap elements
  ... sequential search, sorting
Arrays class
Arrays as arguments & parameters
Arrays of objects
Selection sort
Binary search
2D Arrays
  ... declaring
  ... obtaining number of rows/columns
  ... accessing elements
  ... as arguments & parameters
ArrayList class
  ... Creating and declaring an ArrayList
  ... Diamond syntax <>
  ... Auto-boxing/wrapping

Topics:

What is an array? Why do we need them?

Declaring 1-dimensional arrays. (Here are some old notes on 1D Arrays.)
Accessing array elements
Initializing arrays
- one at a time.
- Using for-loop
- Using brackets
- Using Arrays class.
- Reading from a file. (we'll do this next week)
Printing or Using arrays
- one at a time.
- Using for-loop
- Using an enhanced loop
- Using Arrays class.
Array of primitives vs array of object/references
Swapping elements in an array.
Copying arrays.
Comparing arrays.
Partially filled arrays
Accumulating values in an array.
Arrays as return values and parameters in methods. Arrays are passed by reference. Recall Pass by Value vs Pass by Reference (pdf)
Sorting using Selection Sort
Binary search
ArrayLists: declaring, adding/removing elements, look at method list, copying, wrappers for primitive types
Declaring multi-dimensional arrays. (Here are some old notes on 2D Arrays.)
- Examples: Mazes, Game of Life, TicTacToe
See list of common errors on p. 534 of your text.

In Class Practice Activities

Practice Array problems. Try them on your own. If you can't seem to figure a problem out, look up the solution here.

Object Diagram Practice: Assume there is a Card class defined. Draw the object diagram after each line is executed:

Line  0:   public static void main(String[] args) {
Line  1:      Card[] myCards;
Line  2:      myCards = new Card[4];
Line  3:      for (int i = 0; i < myCards.length ; i++) {
Line  4:         myCards[i] = new Card(i);  
Line  5:         System.out.print(myCards[i] + " "); 
Line  6:      }
Line  7:      Card c = myCards[3];
Line  8:      myCards[0] = myCards[1];
Line  9:      myCards[2] = null;
Line 10:      myCards[3] = null;
Line 11:      myCards[3] = c;
Line 12:      System.out.println("\n");
Line 13:      for (int i = 0; i < myCards.length ; i++) {
Line 14:         System.out.print(myCards[i] + " "); 
Line 15:      }
Line 16:   }

Assuming that the output from Line 5 gives the A♠, 2♠ 3♠ 4♠, what is the output at Line 14?
Solution may be found here: Lines 1-7 and Lines 8-16

paintComponent method