1. SOFTWARE AND PROGRAMMING 1
An AUT action short of strike:
no TEST 2 this year
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Today:
- 2D Arrays

2. 2D arrays: example Example - week sales at each of four shops:
                                      Days         0        1     2      3     4      5      6   | |        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: processing Summary 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
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 Minute
(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]++; }