Java – declare int [] array without defining size?

This is my code:

int[] primes = new int[25];

    for (int i = 2; i <= 100; i++)
    {
        for (int j = i; j > 0; j--)
        {
            int prime = i%j;
            if (prime == 0)
            {
                if ((j == i) || (j == 1))
                {
                    isPrime = true;
                }
                else
                {
                    isPrime = false;
                    break;
                }
            }
        }

        if (isPrime == true){
            primes[index] = i;
            index++;
        }
    }

As you can see, I'm writing prime numbers to an array I calculated all primes in the range of 2-100, so I set the array size to 25

But let's say I didn't know there were 25 primes Is there any way to create an array (any type of array) without defining the size? I tried this:

int[] primes = new int[0];

But it collapsed

Solution

You can use list for data of unknown size (perhaps ArrayList will be your best solution)