textbook example that gives 'Cannot find symbol' error

[jwombles]

New to programming but I've typed this code directly from my text book example yet keep getting a 'Cannot find symbol' error referring to 'DoubleClass' as noted below. Any help is greatly appreciated as always.

DataComparison.java:81: error: cannot find symbol
public static void calculateAverage(Scanner inp, DoubleClass courseAvg)
symbol: class DoubleClass
location: class DataComparison

DataComparison.java:99: error: cannot find symbol
public static void printResult(PrintWriter outp, String courseId, int groupNo, DoubleClass avg)
symbol: class DoubleClass
location: class DataComparison

DataComparison.java:15: error: cannot find symbol
DoubleClass avg1 = new DoubleClass(); //average for a course in group 1
symbol: class DoubleClass

import java.io.*;
import java.util.*;

public class DataComparison
{
	public static void main (String[] args)
									throws FileNotFoundException
	{
					//Step 1
		String courseId1;			//course ID for group 1
		String courseId2;			//course ID for group 2
		
		int numberOfCourses;
		
		DoubleClass avg1 = new DoubleClass();	//average for a course in group 1
		DoubleClass avg2 = new DoubleClass();	//average for a course in group 2
		
		double avgGroup1;		//average group 1
		double avgGroup2;		//average group 2
		
		
					//Step 2 Open the input and output files
		Scanner group1 = new Scanner(new FileReader("group1.txt"));
		Scanner group2 = new Scanner(new FileReader("group2.txt"));
		
		PrintWriter outfile = new PrintWriter("student.out");
		
		
		avgGroup1 = 0.0;					//Step 3
		avgGroup2 = 0.0;					//Step 4
		
		numberOfCourses = 0;
		
				//print heading: Step 6
		outfile.println("Course ID   Group No   Course Average");
		
		while (group1.hasNext() && group2.hasNext())
			{
				courseId1 = group1.next();
				courseID2 = group2.next();
				
				if (!courseId1.equals(courseId2))
				{
					System.out.println("Data error: Course IDs do not match.");
					System.out.println("Program terminates.");
					outfile.println("Data error: Course Ids do not match.");
					outfile.println("Program terminates.");
					outfile.close();
					return;
				}
				else
				{
					calculateAverage(group1,  avg1);
					calculateAverage(group2,  avg2);
					printResult(outfile, courseId1, 1, avg1);
					printResult(outfile, courseId2, 2, avg2);
					avgGroup1 = avgGroup1 + avg1.getNum();
					avgGroup2 = avgGroup2 + avg2.getNum();
					outfile.println();
					numberofCourses++;
				}
			}
			
			if (group1.hasNext() && !group2.hasNext())
				System.out.println("Ran out of data for group 2 before group 1.");
			
			else if (!group1.hasNext() && group2.hasNext())
				System.out.println("Ran out of data for group 1 before group 2.");
			
			else
			{
				outfile.printf("Avg for group 1: %.2f %n", (avgGroup1 / numberOfCourses));
				outfile.prtinf("Avg for group 2: %.2f %n", (avgGroup2 / numberOfCourses));
			}
			
			group1.close();
			group2.close();
			outfile.close();
		}
		
		public static void calculateAverage(Scanner inp, DoubleClass courseAvg)
		{
			double totalScore = 0.0;
			
			int numberOfStudents = 0;
			int score = 0;
			
			score = inp.nextInt();
			
			while (score != -999)
			{
				totalScore = totalScore + score;
				numberOfStudents++;
				score = inp.nextInt();
			}
			
			courseAvg.setNum(totalScore / numberOfStudents);
		}
		public static void printResult(PrintWriter outp, String courseId, int groupNo, DoubleClass avg)
		{
			if (groupNo == 1)
				outp.print("  " + courseId + "   ");
			else 
				outp.print("        ");
				
			outp.printf("%9d %15.2f%n", groupNo, avg.getNum());
		}
	}

[Fou-Lu]

Java does not have a 'DoubleClass' class. There is a 'Double' class, but it doesn't appear to match what you have for methods.
So this is a class you are expected to create yourself.

[jwombles]

Java does not have a 'DoubleClass' class. There is a 'Double' class, but it doesn't appear to match what you have for methods.
So this is a class you are expected to create yourself.

Ok, thanks for the reply. I would not suggest anyone use the Malik Java Programming - From Problem Analysis to Program Design textbook for a beginning Java book.

The reviews on Amazon are horrible and the book does a poor job describing the "why" of what you're doing and there are numerous coding errors and typos that I've come across.