Algorithm to find first n prime number

For second time I found same problem that I can’t solve well when attending job interview. Oh how is so hard become real programmer. The problem is: “Please make algorithm to list all of prime number from 1 to 100″. Ok, I know stupid definition of prime number. A prime can only divide by 1 and itself. For example 3 is prime because it is only divisible by 1 and 3 itself. 4 is not prime. Beside 1 and 4, 4 also divisible by 2. Ok stop talking and show me the code. After trial and error (and try to sneak by googling) I finally can make working method to list all of prime from n number. I write it in Java. Hopefully by writing this I don’t make third mistake. So at another interview I can confidently answer that easy question. Enjoyy.

public void countPrime(int n) {
        boolean flag = true;
        for (int i = 2; i <= n; i++) {// looping through all number
            for (int j = 2; j <= i - 1; j++) {
                // we check each number whether can be divided by other than 1 and itself
                if (i % j == 0) {
                    flag = false; // not prime
                }
            }
            if (flag) { // we print the prime
                System.out.println(i);
            } else {
                flag = true;
            }
        }
    }