//  File: DataSetTester2.java

//  Shows how an input statement can be used as a loop condition!
//  Note: DataSet class is EXACTLY the same as in previous version.
import javax.swing.JOptionPane;

/**
 * Computes statistics for a set of data.
 */
class DataSet2
{
    // instance vars
    private double sum;		// sum of the values in the set
    private int count;		// number of values in the set
    private double maximum;	// largest value

    /**
     * Create an empty data set.
     */
    public DataSet2() {
        count = 0;
        sum = 0;
        maximum = Double.NEGATIVE_INFINITY;	// Java constant
    }

    /**
     * add a value to the data set.
     * @param currentValue the number to be added to the set
     */
    public void add(double currentValue)
    {
        sum = sum + currentValue;     // add new value to the sum
        count++;                      // one more value was added

        if (currentValue > maximum)   // if current value is largest so far...
        {                             // (note: must be true first time)
            maximum = currentValue;   // ...current value becomes new largest
        }
    }

    /**
     * Return the largest value in the set.
     * Note: if set is empty, will return NEGATIVE INFINITY
     * @return the largest value
     */
    public double getMaximum() {
        return maximum;
    }

    /**
     * Return the average of the values in the set.
     * Note: if set is empty, will return INFINITY
     * @return average
     */
    public double getAverage() {
        return sum / count;
    }

    /**
     * Is the set empty?
     * @return true if the set is empty, false if nonempty
     */
    public boolean isEmpty() {
        return count == 0;
    }
}

public class DataSetTester2
{
    public static void main(String[] args)
    {
        DataSet2 set = new DataSet2();	// create an empty data set
        String input;
        String prompt = "Enter a value\n(press Cancel when done)";

        System.out.print("Data entered:  ");

        // loop while more data (i.e., until "end of file")
        while ((input = JOptionPane.showInputDialog(prompt)) != null)
        {
            double value = Double.parseDouble(input);
            System.out.print(value + "  ");
            set.add(value);			// add value to set
        }

        if (set.isEmpty()) // if set is empty, print error message
        {
            System.out.println("ERROR! No data entered!");
        }
        else // set is non-empty, print stats
        {
            System.out.println("\n\nThe average is:\t" + set.getAverage() +
                               "\nThe maximum is:\t" + set.getMaximum())  ;
        }
        System.exit(0) ;
    }
}