Need program to print in decimal format

I need this program to print out the gpa down to 2 decimal places and I can't figure out how to do it. It keeps saying it can't find decimal format and I'm not sure how to define it If you could help me out I'd really appreciate it

Java Code:

import java.util.Scanner;

public class GPACalculator {
    public static void main(String[] args) {
        double creditHours = 0;
        double gradePoints = 0;
        
        System.out.println("Enter number of classes");
        Scanner scanner = new Scanner(System.in);
        double numClass = scanner.nextInt();
        
        for(double i = 1; i <= numClass; i++){
            System.out.println("Enter credit hours for class "+ i);
            double aCreditHour = scanner.nextInt();
            creditHours += aCreditHour;
            System.out.println("Enter grade for class "+ i);
            String letter = scanner.next();
            if(letter.equals("A")){
                gradePoints = gradePoints + (4 * aCreditHour);
            } else if (letter.equals("B")){
                gradePoints = gradePoints + (3 * aCreditHour);
            } else if (letter.equals("C")){
                gradePoints = gradePoints + (2 * aCreditHour);
            } else if (letter.equals("D")){
                gradePoints = gradePoints + (1 * aCreditHour);
            } else if (letter.equals("F")){
                gradePoints = gradePoints + (0 * aCreditHour);
            }
        }
        decimalFormat df = new decimalFormat("#0.00");
        System.out.println("Your GPA is: " + decimalFormat.format(gradePoints / creditHours));
    }
}