Thread: Please, find my mistake

Hey guys, this is the assignment that I should do today:

Write a program to read a list of exam scores given as integer percentages in the range 0 to 100. Display the total number of grades and the number of grades in each letter-grade category as follows: 90-100 is A, 80-89 is B, 70-79 is C, 60-69 is D, and 0-59 is F. Prin the percentage of the total for each letter grade, the lowest, the highest, and average grade. Use negative score as a snetinel value to indicate the end of the input.

For Example, input: 98,87,86,85,85,78,73,72,72,70,66,63,50,-1

Output should be:

Total number pf grades entered was 13

A's =1
B's=4
C's=5
D's=2
F's=1

The % of A's = 7.69&
The % of B's = 30.77%
The % of C's = 38.46%
The % of D's = 15.38%
The % of F's = 7.69&

avg = 75.77
smallest = 50
largest = 98

Here is my code:



import java.util.Scanner;
public class Grades
{
public static void main(String[] args)
{

int numberOFGrades = 0;
double smallest=0, largest=0, average, sum=0;
double grade=1;
int A=0, B=0,C=0,D=0,F=0;
double percentA, percentB, percentC, percentD, percentF;

Scanner scan = new Scanner(System.in);

while (grade<=100 && grade > 0)
{

System.out.println("Please, write your grades ");
grade = scan.nextInt();

if(grade>=90 && grade < 100)
{

A++; // the total of A's


}

else if(grade>=80 && grade < 90)
{

B++; // the total of B's

}
else if(grade>=70 && grade < 80)
{

C++; // the total of C's

}
else if(grade>=60 && grade < 70)
{

D++; // the total of D's
}
else if(grade>=0 && grade <= 59)
{

F++; // the total of F's

}

if (grade >0)
{
numberOFGrades++; // If the grade is negative, It will show the total of grades that was entered

}

}











//the quantity of each grade
System.out.println();
System.out.println("Total of grades entered was " + numberOFGrades);
System.out.println();
System.out.println("Total of A's = " +A);
System.out.println("Total of B's = " +B);
System.out.println("Total of C's = " +C);
System.out.println("Total of D's = " +D);
System.out.println("Total of F's = " +F);

percentA = (A/numberOFGrades)*100;
System.out.println("The percent of A's = " + percentA + "%");
percentB = (B/numberOFGrades)*100;
System.out.println("The percent of B's = " + percentB + "%");
percentC = (C/numberOFGrades)*100;
System.out.println("The percent of C's = " + percentC + "%");
percentD = (D/numberOFGrades)*100;
System.out.println("The percent of D's = " +percentD + "%");
percentF = (F/numberOFGrades)*100;
System.out.println("The percent of F's = " + percentF + "%");





if(grade < 50 && grade>0)
smallest = grade;
if(grade > 90 && grade <=100)
largest = grade;
sum = A + B + C + D + F;
average = (sum/numberOFGrades);
System.out.println("the average is " + average );
System.out.println("the smallest number is " + smallest );
System.out.println("the largest number is " + largest );







}
}

when I input different grades, the percentage is always 0, but when I input the same grade, this grade just shows 100%

Also, I don't know how to find average, and this stuff

while (grade<=100 && grade > 0)

This won't work if grade is 0 exactly.

while (grade<=100 && grade >= 0)

is better.


This probably isn't going to be code that you can use directly, but it might help

(Also, are you allowing extra credit? i.e. what if someone got a 105?)

Assuming no extra credit,

if (grade <=100 && grade >=90)
letter = 'A';
else if (grade >=80 && grade <=89)
letter = 'B';
else if (grade >=70 && grade <=79)
letter = 'C';
else if (grade >=60 && grade <=69)
letter = 'D';
else if (grade >=0 && grade <=59)
letter = 'F';
else
letter = '?';


percentA = (A/numberOFGrades)*100;

That is the result of an annoying thing in java,

for instance

double value3 = (11/5) * 100;

will return 200, not 250.

One way to make it be a double

double value3 = (double)(11)/(double)(5) * 100;

value3 is now 220.00000000000003;

I think you can use the DecimalFormat class to fix it to be two digits after the decimal.

Thanks a lot for your reply!

I will try it now, and if it works I will let you know!

Oh God! It works... so we have to convert integers to doubles first! Wow! Thank you so much...

Do you know how to find smallest, average, and largest grade ? Please, let me know... I am just a beginner, I am really sorry about that

Is grade meant to be entered as a double, i.e. a decimal, or as an integer?

double grade=1;
grade = scan.nextInt();


if it's a double, then a better way of putting that would be
grade = scan.nextDouble();

Write a program to read a list of exam scores given as integer percentages in the range 0 to 100

I followed all your steps, and everything works except "the smallest".. it's still becomes the negative number... what the problem?

Thanks a lot for your help! I have already written the program and it actually worked.. I used the DecimalFormat class as you said before!

Thanks a lot! I really appreciate it...

So how to make it as "solved"?