java - Trying to calculate the average of inputs given using do-while and while loop but it keeps stopping -

the main gist of script keep asking grades until user inputs negative number. once negative number has been input, calculates average of grades. grade input user can 4-10.

i've been hours trying figure out.. if enter invalid inputs or valid inputs works fine, second try mix script stops.

for example: if enter 4(valid input) script asks grade. if enter 3(invalid input) script says input invalid , asks valid input. after if enter 4 again stops working, when supposed keep going until enter negative number make start calculating average of valid inputs.

import java.util.scanner;  public class average {  public static void main(string[] args){      scanner scanner = new scanner(system.in);  system.out.println("the program calculate average of user inputted grades."); system.out.println("the program start calculating negative integer");  double grade;    double sum = 0; int count = 0;    {     system.out.print("input grade (4-10): ");     grade = scanner.nextdouble();      if (grade >= 4 && grade <= 10){         sum = sum + grade;         count++;      }    } while (grade >= 4 && grade <= 10);   {   while (grade >= 0 && grade < 4 || grade > 10){      system.out.println("invalid grade!");     system.out.print("input grade (4-10): ");     grade = scanner.nextdouble();       if (grade < 0){          system.out.println(count + " grades given.");         system.out.println("average: " + sum/count);         break;     }   }  } }  

it doesn't work because loops separated, if first false, second works once , stops. try this:

import java.util.scanner;  public class average {      public static void main(string[] args){          scanner scanner = new scanner(system.in);          system.out.println("the program calculate average of user inputted grades.");         system.out.println("the program start calculating negative integer");          double sum = 0;         int count = 0;         double grade;          do{             system.out.print("input grade (4-10): ");             grade = scanner.nextdouble();              if(grade >= 4 && grade <= 10){                     sum = sum + grade;                     count++;             }else{                 system.out.println("invalid grade!");             }         }while(grade >= 0);          system.out.println(count + " grades given.");         system.out.println("average: " + sum/count);       } }