SOFTWARE AND PROGRAMMING 1

An AUT action short of strike:

no TEST 2 this year

_________________________Today:

- 2D Arrays

2

2D arrays: example

Example - week sales at each of four shops:  

                                      Days         0        1     2      3     4      5      6   |---------------------------------------------------- 0|        22     49     4     93     0     12     32   | 1|         3        8     67   51     5      3     63 |2|         14      8     23   14     5     23     16   | 3|         54      0     76   31     4      3     99

3

2D arrays: actions

Declaration and initialisation (with zeros):  int[ ][ ] sales = new int[4][7];

   Filling in: sales = {

                {22, 49, 4, 93, 0, 12, 32},                   ………………………,

                {54, 0, 76, 31, 4, 3, 99}               }

4

2D arrays: accessing

Reaching a component: sales[2][5] = 23 or int aa = 2; int bb = 5; sales[aa][bb]=23 sales[bb][aa] = ? (answer:

error)  

5

2D arrays: processingSummary sales: •     int sum =0; •     for (int shop = 0; shop < 4; shop ++) •     for(int day = 0; day < 7; day ++) •     sum = sum + sales[shop][day]; As a method:  public int sum( int[][] a) { •  int total = 0; • for (int row = 0; row < a.length; row ++) •  for( int col = 0; col < a[0].length; col ++) •  total = total + a [row][col]; •                     return total;               }

6

2D arrays: different row lengths

Different row lengths: int[ ] Twodarray={{1, 1, 1}, {1, 3}, {4,5,4,5}}Modifying the summation method:  public int sum( int[][] a) { •  int total = 0; • for (int row = 0; row < a.length; row ++) •   for( int col = 0; col < a[row].length; col

++) •   total = total + a[row][col]; •         return total;               }

• int summa=sum(Twodarray);

7

Two-dimensional arrays

Summary sales for Wednesday: •         int sum =0; •         for (int row=0; row< 4; row

++) •         sum = sum + sales[row][2]; Further problems: • methods:

– summary sales by week-day– summary sales by shop

• methods for finding the minimum and the maximum

8

Log counts in LogAnalyzer (Chapter 4.11 BlueJ book)

Part of a real log file in a web server (register of accesses), weblog.txt

Year Month Day Hour Minute2002 5 22 22 432002 5 22 22 432002 5 22 23 582002 5 23 00 162002 5 23 00 162002 5 23 03 53. . . . . . . . . . . . . . . . . . . . . . .(3749 rows of May 2002)

9

Log counts in LogAnalyzer (Chapter 4.11 BlueJ book)

BlueJ project “weblog-analyzer” consists of four classes:

LogfileReader reads a log file

LogEntry reads a line from the log file

LoglineTokenizer tokenizes a line into its constituting items

LogAnalyzer counts statistics from line items

10

Original LogAnalyzer (Chapter 4.11 BlueJ book, p. 101)

- public class LogAnalyzer { private int[] hourCounts; //Hourly access counts.

private LogfileReader reader; // to access the data public LogAnalyzer() //constructor {hourCounts = new int[24]; // array for the hourly access

counts reader = new LogfileReader(); // Reader to obtain the data- }

public void analyzeHourlyData()- { while(reader.hasMoreEntries()) {- LogEntry entry = reader.nextEntry();- int hour = entry.getHour();- hourCounts[hour]++; }- }- }

11

2D month-hour log counts in LogAnalyzer

This method in LogAnalyzer should be updated for the purpose: public void analyzeHourlyData()

{ while(reader.hasMoreEntries()) { LogEntry entry = reader.nextEntry(); int hour = entry.getHour();//getHour, a method in LogEntry to get hour hourCounts[hour]++; } }

12

2D month-hour counts with LogAnalyzer (2)

We need a method in class LogEntry for getting month as well, to be added:

public int getMonth() { return dataValues[Month]; }//dataValues is the array in LogEntry

holding //all five data entries (year,…,minute)

13

2D month-hour log counts in LogAnalyzer

Now - an analogue to analyzeHourlyData: public void analyzeHourMonthlyData() { while(reader.hasMoreEntries()) { LogEntry entry = reader.nextEntry(); int hour = entry.getHour(); int month=entry.getMonth();//getHour, a method in LogEntry to get hour hourmonthCounts[month][hour]++; } }//hourmonth[ ][ ] must be declared and //initialized beforehand

14

2D Modified LogAnalyzer

- public class LogAnalyzer { private int[][] hourmonthCounts; //Hour-Monthly access counts.

private LogfileReader reader; // to access the data public LogAnalyzer() //constructor {hourmonthCounts = new int[24][12]; // h.-monthly access

counts reader = new LogfileReader(); // Reader to obtain the data- }

public void analyzeHourMonthlyData()- { while(reader.hasMoreEntries()) {- LogEntry entry = reader.nextEntry();- int hour = entry.getHour(); int month = entry.getMonth();

//method getMonth() must be added to LogEntry- hourmonthCounts[hour][month]++; }- }- }