incrementing int variable in for loop java

Question

Guys I am trying to understand why we have incremented frequency and divided grade by 10 could somebody please help explain.

public void getBarChart(){

    System.out.println("\nGrade Distribution: ");

    int[] frequency = new int[11];

    for (int grade : grades)
        ++frequency[grade / 10];

    for (int counter =0 ; counter < frequency.length; counter++){


        if(counter == 10){

            System.out.printf("%5d:  ",100);
        }

        else{

            System.out.printf("%02d-%02d: "
                    ,counter * 10, counter * 10 + 9 );
        }

        for (int stars= 0; stars < frequency[counter] ; stars++)
            System.out.print("*");

        System.out.println();
    }
}

It is storing the amount of grades that it finds in a certain range. Imagine the value of grade is 78, then it will increment to number in the seventh element of the frequency array — Scary Wombat
– Scary Wombat, Commented Oct 24, 2017 at 8:51
@inoxy probably the line where he "... incremented frequency and divided grade by 10 ..." like it says in the question. — Dawood ibn Kareem
– Dawood ibn Kareem, Commented Oct 24, 2017 at 8:51

Eran · Accepted Answer · 2017-10-24 08:52:33Z

3

Assuming grade can be between 0 and 100, the frequency array counts how many grades fall in the groups 0-9, 10-19, ..., 90-99, 100.

That's the reason you divide grade by 10 to locate the array index.

++frequency[grade / 10] increments the count of grades that fall in the group of that grade.

So, for example, the grade 75 will be counted in the array element frequency[75 / 10] which is frequency[7]. frequency[7] will contain the number of grades in the range 70 to 79.

answered Oct 24, 2017 at 8:52

Eran

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