Which of the following is an invalid syntax to initialize an array of integers?
int[] a;
a = { 1, 2, 3 };
int[] a = { 1, 2, 3 };
int[] a = new int[] { 1, 2, 3 };
int[] a = new int[3];
a[0] = 1;
a[1] = 2;
a[2] = 3;