Too many 'if' statements?

Question

The following code does work how I need it to, but it\'s ugly, excessive or a number of other things. I\'ve looked at formulas and attempted to write a few solutions, but I

Answer 1

Why not use an array?

I will start from the beginning. I see a pattern, the values goes from 0 to 3 and you want catch all possible values. This is your table:

0 & 0 = 0
0 & 1 = 0
0 & 2 = 1
0 & 3 = 2
1 & 0 = 0
1 & 1 = 0
1 & 2 = 2
1 & 3 = 1
2 & 0 = 2
2 & 1 = 1
2 & 2 = 3
2 & 3 = 3
3 & 0 = 2
3 & 1 = 1
3 & 2 = 3
3 & 3 = 3

when we look at this same table binary we see the following results:

00 & 00 = 00
00 & 01 = 00
00 & 10 = 01
00 & 11 = 10
01 & 00 = 00
01 & 01 = 00
01 & 10 = 10
01 & 11 = 01
10 & 00 = 10
10 & 01 = 01
10 & 10 = 11
10 & 11 = 11
11 & 00 = 10
11 & 01 = 01
11 & 10 = 11
11 & 11 = 11

Now maybe you already see some pattern but when I combine value one and two I see that you're using all values 0000, 0001, 0010,..... 1110 and 1111. Now let's combine value one and two to make a single 4 bit integer.

0000 = 00
0001 = 00
0010 = 01
0011 = 10
0100 = 00
0101 = 00
0110 = 10
0111 = 01
1000 = 10
1001 = 01
1010 = 11
1011 = 11
1100 = 10
1101 = 01
1110 = 11
1111 = 11

When we translate this back into decimal values we see an very possible array of values where the one and two combined could be used as index:

0 = 0
1 = 0
2 = 1
3 = 2
4 = 0
5 = 0
6 = 2
7 = 1
8 = 2
9 = 1
10 = 3
11 = 3
12 = 2
13 = 1
14 = 3
15 = 3

The array is then {0, 0, 1, 2, 0, 0, 2, 1, 2, 1, 3, 3, 2, 1, 3, 3}, where it's index is simply one and two combined.

I'm not a Java programmer but you can get rid of all if statements and just write it down as something like this:

int[] myIntArray = {0, 0, 1, 2, 0, 0, 2, 1, 2, 1, 3, 3, 2, 1, 3, 3};
result = myIntArray[one * 4 + two]; 

I don't know if a bitshift by 2 is faster than multiplication. But it could be worth a try.