ch06/dataset/DataSet.java
 /**
 Computes information about a set of data values.
 */
 public class DataSet
 {
 /**
 Constructs an empty data set.
 */
 public DataSet()
 {
 sum = 0;
 count = 0;
 maximum = 0;
 }
 /**
 Adds a data value to the data set.
 @param x a data value
 */
 public void add(double x)
 {
 sum = sum + x;
 if (count == 0 || maximum < x) maximum = x;
 count++;
 }

 /**
 Gets the average of the added data.
 @return the average or 0 if no data has been added
 */
 public double getAverage()
 {
 if (count == 0) return 0;
 else return sum / count;
 }

 /**
 Gets the largest of the added data.
 @return the maximum or 0 if no data has been added
 */
 public double getMaximum()
 {
 return maximum;
 }

 private double sum;
private double maximum;
 private int count;
}