Thread: Need help

Okay In my class we just learned arrays and boy am i lost anyways i got stuck in my lab I don't understand it.

Write program Lab11.java which reads integer grades until the user enters the sentinel -1. As you read the grades, store them in an integer array. You can assume each grade is on the range 0..100. Afterwards, your program:
● should sort the grades read in increasing order. Use the Bubble Sort algorithm that we covered in class to sort the grades in increasing order;
● should compute the mode, median, average, and the standard deviation σ of the grades;
● should determine how many grades fall within one standard deviation σ from the average, i.e., how many grades are in the range (average – σ)…(average + σ);
● should print the sequence of grades in increasing order.
Remember that:
● The mode is the grade that appears the most number of times.
● The median is the grade that appears right in the middle of the sequence of increasingly sorted grades.
● The average is the sum of all the grades divided by the number of grades.
●The formula for the standard deviation σ is the following:
n-1
Standard deviation σ = 1 Σ (gradei – average)2
√ n-1 i=0
where n is the number of grades.

Ok so how do I take user input for the array for a unknown size??

i no it's first a while loop because its a sentinel control loop, and have to import scanner from there I draw a blank. Also I haven't done mode before.

Create an array of some reasonable size, not too big and not too small.
Keep track of how many values have been added to the array.
When it is full create a new array of a larger size. Once again a reasonable size. If you increase by one you will be doing a lot of overhead if there are another 100 values to be inserted.
Copy all values from old array into new array.
Add new value.
Set array variable to refer to new array.

an easy solution wud be ArrayList

import java.util.Scanner ;
import java.util.ArrayList ;
class Whatever{
    public static void main(String [] args){
         Scanner s = new Scanner(System.in) ;
         ArrayList<Integer> al = new ArrayList<Integer>() ;
         while(s.hasNext()){
            int ii = s.nextInt() ;
            if (ii == -1) break ;
            al.add(ii) ;
         }
        int [] arr = al.toArray(new int[al.size()]);
   }
}

Hope this helps...
But this is usually a overhead when u frequntly need to convert arraylist to array. B.O.L.

Originally Posted by dumb_terminal

an easy solution wud be ArrayList
Hope this helps...

You mean "would". Please spell words out in full, especially if English is not your first language. No it doesn't help as the instructions explicitly said to use an array not a List

import.util.Scanner;

public class Lab11
{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in)

int grade = 0, total = 0, sum = 0;

while (grade != -1);
{
System.out.println("Enter grade. When done enter -1")
grade = scan.nextInt();
total = total + grade
sum = sum + 1
}

// bubble sort
int i, j;

for(i = 1; i <= sum; i = i + 1)
for(j = 0; j <= sum -1 - i; j = j + 1)
if(array[j] > array[j + 1]
{
temp = array[j];
array[j] = array[j + 1];
array[j + 1] = temp;
}

// average
int index;
double avg;

for(index = 0; index < total; index = index + 1)
if sum > 0 sum = sum + array[index]
{
avg = (double)total/sum
return avg;
}
else
return does not compute;





}
}

this is what i have so far sorry I have been busy with other stuff so i haven't complied because my computer will not let me. Anyways can you spot any errors i need to fix

Thanks, but an array list doesnt help if i dont understand arrays still. My professor is not very good at teaching so I am trying to learn on my own and I'm not doing such a great job.

Originally Posted by KevinWorkman

Your first step is to get a compiler working then.

im going to my school to do so but before then trying to get as little errors as possible before I ask my old professor for some help and tips