1. Collections behaviour and implementation of collections of primitives and objects

2. D. Goforth, COSC 3106, fall 20032 Arrays – of primitive types  arrays are objects array variables contain references to arrays int[] x = new int[5]; x[2] = 550; // indexing starts at 0 x 0005500

3. D. Goforth, COSC 3106, fall 20033 Arrays – of objects  arrays of object types array variables contain references to arrays of references String[] y = new String[5]; y[2] = “Hello”; y Hello

4. D. Goforth, COSC 3106, fall 20034 Arrays accessing individual elements  find size of array with length variable int[] x = new int[5]; x[2] = 550; int number = x.length;//number contains 5  index range: 0 to length-1 x[0] = 100; x[4] = -20; x[5] = 1000; // ArrayIndexOutOfBoundsException thrown

5. D. Goforth, COSC 3106, fall 20035 Partly filled arrays  problem with collection of items that changes in size eg list of paddleboats for rental inventory is 10 boats but number available varies between 0 and 10 use array of integers to store identity numbers of boats available

6. D. Goforth, COSC 3106, fall 20036 Partly filled arrays  array length is fixed  data is always at front of array  use an integer counter to track how many data items are in the array x 701680550-320 xCount 4 00050109

7. D. Goforth, COSC 3106, fall 20037 Partly filled arrays  when new data is added to next location, count is increased x 70168550-320 xCount 5 00050109 x 701680550-320 xCount 4 00050109 112

8. D. Goforth, COSC 3106, fall 20038 Partly filled arrays  example – BoatCollection inventory collection of boats that are rented out and returned BoatCollection.html BoatCollection.java

9. D. Goforth, COSC 3106, fall 20039 Multi-dimensional arrays  to represent matrices, tables, calendar months, patch arrays  e.g., distance chart Sudbury0 Toronto1 Ottawa2 Sudbury Toronto Ottawa 0 12 0400500 4000600 5006000

10. D. Goforth, COSC 3106, fall 200310 Multi-dimensional arrays int[][] m = new int[3][4]; m[2][3] = -60; 012012 0 12 3 000 000 000 0 0 -60

11. D. Goforth, COSC 3106, fall 200311 Review of some array operations  first question: entire array or ‘real’ data subset?  sum of data  maximum value  range of data  increment every value  search for value