int[] arr = {1,2,2,3,4,5,5};

if (arr[0] != arr[1]) System.out.print(arr[0] + " ");
for (int i = 1; i < arr.length - 1; i++){
if(arr[i-1] != arr[i] && arr[i+1] != arr[i]){
System.out.print(arr[i] + " ");
    }
}
if (arr[arr.length-1] != arr[arr.length-2]) System.out.print(arr[arr.length-1] + " ");