A perfect number is a number that's equal to the sum of all its positive divisors, excluding itself.
For my homework, I'm trying to write a program to find all four perfect numbers under 10000, but my code doesn't work when I run it and I'm not sure why (it just runs for a second or two, and then says "build successful" after not printing anything). I included it below, along with some comments that explain my thought process. Can someone help me out and tell me what's wrong with it?
public class HomeworkTwo {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
//Variable declaration
int n;
int possibleFactor;
int factorSum=0;
/**For each n, the program looks through all positive integers less than n
and tries to find factors of n. Once found, it adds them
together and checks if the sum equals n. Then it repeats till n=9999. **/
for (n=2; n<10000; n++) {
for (possibleFactor = 1; possibleFactor < n; possibleFactor++) {
if (n % possibleFactor == 0) {
factorSum = possibleFactor + factorSum;
}
//Is the number perfect? Printing
if (factorSum == n) {
System.out.println(""+ n +" is a perfect number.");
}
}
}
}
}
You initialize factorSum to 0 before the first for loop, but you don't reset it to 0 when trying each new n. The factors keep adding up and are never equal tot he number to check. Reset it to 0 at the beginning of the n for loop.
Also, you may want to move the test and print of the number being a perfect number after the inner for loop, but before the end of the outer for loop, or else it may print more than necessary.