Finding prime numbers

I have this code as an implementation of the 'Sieve of Eratosthenes'. But either it is super duper slow or it doesn't work. What is wrong with it?

p.s. I am finding all the primes numbers in a sorted array with numbers 1-100 inclusive.

Code:

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public void sievePrimes()
{ 
    numbers[0] = 0;
    int n = numbers[99];
 
    for(int i=1; i<n; i++)
    {
        numbers[i] = 1;   
    }
    int p = 2;
    while(p*p <= n)
    {
        int j = p*p;   
        while(j <=n)
        {
            numbers[j-1] = 0;
            j = j+p;
        }
        while(numbers[p] != 1)
        {
            p++; 
        }
    }
    for(int index=0; index < numbers.length; index++)
    {
        System.out.println(numbers[index]);   
    }
}

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while (j <= n) {
numbers[j - 1] = 0;
j = j + p;
}
Doesn't stop looping

Quote:

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Originally Posted by ComputerJy

while (j <= n) {
numbers[j - 1] = 0;
j = j + p;
}
Doesn't stop looping

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How can i stop it from doing that and work correctly?

This is the psuedo code algorithm.

Code:

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Eratosthenes(n) {
  a[1] := 0                         
  for i := 2 to n do a[i] := 1
  p := 2
  while p2  <  n do {
    j := p2
    while (j  <  n) do {           
      a[j] := 0
      j := j+p
    }
    repeat p := p+1 until a[p] = 1 
  }
  return(a)
}

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This is the algorithm as I know it:

Code:

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public class Sieve {
  private static int upperLimit = 1000;
  private static boolean[] flags;
  public Sieve() {}

  public static void main(String[] args) {
    initialize(args);
    findPrimes();
    displayPrimes();
  }

  private static void initialize(String[] args) {
    if (args.length > 0) {
      upperLimit = Integer.parseInt(args[0]);
    }
    flags = new boolean[upperLimit + 1];
    for (int position = 0; position <= upperLimit; position++) {
      flags[position] = false;
    }
  }

  private static void findPrimes() {
    for (int position = 2; position <= Math.sqrt(upperLimit); position++) {
      if (!flags[position]) {
        int multiple = position * 2;
        while (multiple <= upperLimit) {
          flags[multiple] = true;
          multiple += position;
        }
      }
    }
  }

  private static void displayPrimes() {
    for (int position = 2; position <= upperLimit; position++) {
      if (!flags[position]) {
        System.out.print(position + ", ");
      }
    }
  }
}

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