from How to mix two arrays in Java?How to mix two arrays in Java?
int[] merge(int[]... arrays) { int length = 0; for (int[] a: arrays) { length += a.length; } int result[] = new int[length]; for (int i = 0, j = 0; j < length; ++i) { for (int[] a: arrays) { if (i < a.length) { result[j++] = a[i]; } } } return result; } then simply
merge(list1, list2, list3)