Cannot figure out error messages

Code:

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Gpa.java:31: incompatible types
found  : boolean
required: double
            gpa = scan.hasNextDouble();
                                    ^

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I don't exactly know why this is, or how to fix it. (I honestly get this error message any time I use scan.hasNext() ) When I change this to scan.nextDouble() I get this when I run my program:

Code:

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Exception in thread "main" java.util.InputMismatchException
        at java.util.Scanner.throwFor(Scanner.java:857)
        at java.util.Scanner.next(Scanner.java:1478)
        at java.util.Scanner.nextDouble(Scanner.java:2404)
        at Gpa.main(Gpa.java:31)

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And it's at the same (Gpa.java:31) line as where I got the first error. What do I need to do?

Code:

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public class Gpa
{
  public static void main(String[] args)
  {
      Scanner scan = new Scanner(System.in);
      DecimalFormat fmt = new DecimalFormat("0.00");
      boolean groupName;
      final String SENT = "EndOfGroup";
      String stuName;
      int groupCount, numGroup;
      double groupMin, groupMax, gpaAverage, gpa, groupSum;
      while(scan.hasNext())
      {
        groupName = scan.hasNextLine();
        numGroup = 0;
        groupSum = 0;
        groupCount = 0;
        groupMin = 0.0;
        groupMax = 4.0;
        gpaAverage = 0;

        stuName = scan.next();
        while(!stuName.equals(SENT))
        {
            numGroup++;
            gpa = scan.nextDouble();
            groupSum = groupSum + gpa;
            groupCount++;
            if(gpa >= groupMin)
            {
              groupMin = gpa;
            }
            if(gpa <= groupMax)
            {
              groupMax = gpa;
            }

            gpaAverage = groupSum/numGroup;
            System.out.print("Student: "+stuName);
            System.out.print("                GPA = "+fmt.format(gpa));
            stuName = scan.next();

        }

        System.out.println("Average GPA for this group = "+fmt.format(gpaAverage));
        System.out.println("Minimum GPA for this group = "+fmt.format(groupMin));
        System.out.println("Maxium GPA for this group = "+fmt.format(groupMax));




  }

}

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Scanner#hasNextXXX() only checks to see if the next token exists and is of type XXX. It doesn't retrieve the token itself which is the job of the nextXXX() method (note that XXX can be Double, Boolean, Int, etc...).

Here you declare variable gpa as a double:

Code:

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double groupMin, groupMax, gpaAverage, gpa, groupSum;

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And here you attempt to assign a boolean value to it (see this for details):

Code:

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gpa = scan.hasNextDouble();

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The reason you are getting an error with gpa = scan.nextDouble(); is that the input received is not a float data. For example, if the scanner's next token was "ABC", it would throw this error. What data are you feeding to it?

Edit: Beaten. :(

The input Im trying to feed into that variable are all numbers in the form of X.XXX (3.756, 2.394, etc).

Quote:

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Originally Posted by Teclis

The input Im trying to feed into that variable are all numbers in the form of X.XXX (3.756, 2.394, etc).

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Fair enough, but do you understand what we are trying to tell you? If not, please let us know just what is unclear.

I think I understand what your saying. It's just that I don't understand how to correct it so that I can read 3.765 into double gpa.

Again you use scan.hasNextDouble() to see if a double is available and you use scan.nextDouble() to actually get the double value from the user. Please try to incorporate this into your code and see what happens. If it still doesn't work, please post your latest attempt, any error messages and let's see what we can fix.