[JAVA] Big Integer to Binary

[donchen]

Anyone can show me how to convert a BigInteger to Binary ?

I know the int class has a method to convert to binary but I need to use BigInteger to convert binary.

[Antaris Veteran]

BigInteger does contain a radix feature, allowing you to supply the base-radix number for the instance:

BigInteger myInt = new BigInteger("12");
String binaryString = myInt.toString(2);

The toString() method can take an integer argument to represent the radix value (the base-radix value, e.g. base-2, base-10, base-16 etc). When the method runs, it will convert the number into the binary representation, so the above example should output the myInt value as the binary representation of 12 = '11000'.

I haven't done java in a while (it's mainly because I hate it), so I could be wrong!

[rpgfan]

You can also do the same thing to take a binary integer and make it a BigInteger:

String binaryString = "1010110101011010101010101101010101100101011010001010001100101110";
BigInteger bigInt = new BigInteger(binaryString, 2);

Untested, but according to the docs, it should work. That constructor has been there since J2SE 1.3 at least. :)

[donchen]

yes.. it works.. thanks alot!

[zackiv31]

12 = '1100'

but his suggestion looks good anyway

[Antaris Veteran]

Ooops, typo :p

[monkey13]

Look out its the binary police. Did someone call 1001 1001 1001 ?

[rpgfan]

You mean 100100010001? :p

[Mike Mayer]

1001 0001 0001 is how you get the binary police..... :)

[zackiv31]

[geeks]there are only 10 types of .... [/geeks]

[monkey13]

Not here in the 01010101.01001011

[rpgfan]

  zackiv31 said:

[geeks]there are only 10 types of .... [/geeks]

[geeks][baltern]There are only +- people that understand balanced ternary - those understand it, those who don't care.[/baltern][/geeks]

[primexx]

  rpgfan said:

[geeks][baltern]There are only +- people that understand balanced ternary - those understand it, those who don't care.[/baltern][/geeks]

care to explain?

[rpgfan]

  Primexx said:

care to explain?

I could, but Wikipedia explains it so much better - http://en.wikipedia.org/wiki/Balanced_ternary

Simply put, there are three values, like in normal (unbalanced) ternary: -1, 0 and 1, which are easily represented using '-', '0' and '+' respectively.

The idea is the same as in any base. Multiply the place value by the value at that place and do the same for the rest. Then add them up. Example:

+-0- (balanced ternary) to decimal:

+ x 3^3 = 1 x 3^3 = 1 x 27 = 27
- x 3^2 = -1 x 3^2 = -1 x 9 = -9
0 x 3^1 = 0 x 3^1 = 0 x 3 = 0
- x 3^0 = -1 x 3^0 = -1 x 1 = -1

(27) + (-9) + (0) + (-1) = 18 + -1 = 17

Strange? Not really. Also, there is no need for a sign bit, unlike binary. -+ is -3 + 1 = -2. However, if you thought of the '-' as a sign bit like it is in binary, then wouldn't it really be ------...---+ ? But then you're subtracting A LOT, not just denoting a sign. So techically, you can write -+ as 000000...00-+. The same is true for positive numbers as well. In other words, all values would be unsigned, and positive and negative values could be represented equally!