public DataSet(Measurer ameasurer) { sum = 0; count = 0; minimum = null; maximum = null; measurer = ameasurer; }

Transcription

1 9.5) Computes the average of a set of data values. public class DataSet private double sum; private Object minimum; private Object maximum; private int count; private Measurer measurer; public DataSet(Measurer ameasurer) sum = 0; count = 0; minimum = null; maximum = null; measurer = ameasurer; public void add(object x) sum = sum + measurer.measure(x); if (count == 0 measurer.measure(minimum) > measurer.measure(x)) minimum = x; if (count == 0 measurer.measure(maximum) < measurer.measure(x)) maximum = x; count++; public double getaverage() if (count == 0) return 0; else return sum / count; public Object getmaximum() return maximum;

2 public Object getminimum() return minimum; Describes any class whose objects can measure other objects. public interface Measurer double measure(object anobject); Objects of this class measure rectangles by area. public class RectangleMeasurer implements Measurer public double measure(object anobject) Rectangle arectangle = (Rectangle) anobject; double area = arectangle.getwidth() * arectangle.getheight(); return area; This program demonstrates the use of a Measurer. public class DataSetTester Measurer m = new RectangleMeasurer(); DataSet data = new DataSet(m);

3 data.add(new Rectangle(5, 10, 20, 30)); data.add(new Rectangle(10, 20, 30, 40)); data.add(new Rectangle(20, 30, 5, 15)); System.out.println("Average area: " + data.getaverage()); System.out.println("Expected: 625"); Rectangle min = (Rectangle) data.getminimum(); System.out.println("Minimum area rectangle: " + min); System.out.println("Expected: java.awt.rectangle[x=20,y=30,width=5,height=15]"); 9.6) This program tests the measurement of rectangles by perimeter. public class PerimeterTester DataSet data =...; data.add(new Rectangle(5, 10, 20, 30)); data.add(new Rectangle(10, 20, 30, 40)); data.add(new Rectangle(20, 30, 5, 10)); double avg =...; Rectangle max =...; System.out.println("Average perimeter: " + avg); System.out.println("Expected: "); System.out.println("Largest perimeter: " + max); System.out.println("Expected: "); public class PerimeterMeasurer implements Measurer

4 public double measure(object anobject) Rectangle arectangle = (Rectangle) anobject; double perimeter = (2 * arectangle.getwidth()) + (2 * arectangle.getheight()); return perimeter; 9.7) Describes any class whose objects can be measured. public interface Measurable Computes the measure of the the measure double getmeasure(); Describes any class whose objects can measure other objects. public interface Measurer Computes the measure of an anobject the object to be the measure double measure(object anobject); This program tests a data set that can be used with measurers and measurables. public class DataSetTester

5 class RectangleMeasurer implements Measurer public double measure(object anobject) Rectangle arectangle = (Rectangle) anobject; double area = arectangle.getwidth() * arectangle.getheight(); return area; Measurer m = new RectangleMeasurer(); DataSet d = new DataSet(m); d.add(new Rectangle(5, 10, 20, 30)); d.add(new Rectangle(10, 20, 30, 40)); d.add(new Rectangle(20, 30, 5, 10)); System.out.println("Average area: " + d.getaverage()); System.out.println("Expected: "); Object max = d.getmaximum(); System.out.println("Largest area: " + m.measure(max)); System.out.println("Expected: 1200"); // Test the default Measurer d = new DataSet(); d.add(new BankAccount(2000)); d.add(new BankAccount(200)); d.add(new BankAccount(20000)); System.out.println("Average balance: " + d.getaverage()); System.out.println("Expected: 7400"); Measurable max2 = (Measurable) d.getmaximum(); System.out.println("Highest balance: " + max2.getmeasure()); System.out.println("Expected: 20000");

6 9.11) public class FirstDigitDistribution private int[] counters; public FirstDigitDistribution() counters = new int[10]; public void process(sequence seq, int valuestoprocess) for (int i = 1; i <= valuestoprocess; i++) int value = seq.next(); while (value > 9) value /= 10; counters[value]++; Displays the counter values of this distribution. public void display() for (int i = 0; i < counters.length; i++) System.out.println(i + ": " + counters[i]); public class RandomSequence implements Sequence public int next() return (int) (Integer.MAX_VALUE * Math.random()); public interface Sequence

7 int next(); public class SequenceDemo FirstDigitDistribution dist1 = new FirstDigitDistribution(); dist1.process(new SquareSequence(), 1000); dist1.display(); System.out.println(); FirstDigitDistribution dist2 = new FirstDigitDistribution(); dist2.process(new RandomSequence(), 1000); dist2.display(); public class SquareSequence implements Sequence private int n; public int next() n++; return n * n;