Arranging Array

Question

Any algorithm suggestion?
As you see, task is putting all 9s next to 4(for each 4 there is one 9)
I did, but it just rearranges last 9.
Thank you in advance!

import java.util.Arrays;

public class Task4 {

public static void main(String[] args) {
int [] nums1 = {1,4,1,9};
int [] nums2 = {1,4,1,9,9,4,1};
int [] nums3 = {4,2,2,9};

nums1 = order49(nums1);
nums2 = order49(nums2);
nums3 = order49(nums3);

System.out.println(Arrays.toString(nums1)); // [1,4,9,1]
System.out.println(Arrays.toString(nums2)); // [1,4,9,1,1,4,9]
System.out.println(Arrays.toString(nums3)); // [4,9,2,2]
}

public static int[] order49(int[] a) {
for (int i = 0; i < a.length; i++) {
if (a[i] == 4) {
for (int j = 0; j < a.length; j++) {
if (a[j] == 9)
swap(a, i + 1, j);
}
}

}

return a;
}

public static void swap(int[] a, int p1, int p2) {
int temp = a[p1];
a[p1] = a[p2];
a[p2] = temp;
}

}

Answer 1

This algorithm gives an IndexOutOfBoundException if the 4 is the last integer in the array