No—each group can have a different number of students in it.
Here is a start on coding the program:
import java.io.*; class TestGroups { public static void main ( String[] args ) throws IOException { String line; BufferedReader stdin = new BufferedReader( new InputStreamReader( System.in ) ); int value; // the value of the current integer // Group "A" int sizeA; // the number of students in group "A" int sumA = ___; // the sum of scores for group "A" System.out.println("How many students in group A:"); line = stdin.readLine(); sizeA = Integer.parseInt( line.trim() ); int count = _______; // initialize count while ( count < ________ ) { System.out.println("Enter a number:"); line = stdin.readLine(); value = Integer.parseInt( line.trim() ); ___________________ ; // add to the sum ___________________ ; // increment the count } if ( sizeA > 0 ) System.out.println( "Group A average: " + ___________________ ); else System.out.println( "Group A has no students" ); // Group "B" . . . . more code will go here . . . . } }