BigInteger.valueOf() for very big numbers?

问题

What would be the best way to convert a 50-digit String to a BigInteger in Java? It doesn't have a valueOf(String) method, and I can't convert to Long because it's too small.

回答1:

It does have a BigInteger(String) constructor :-)

String S = "12345678901234567890123456789012345678901234567890";
BigInteger bi = new BigInteger(S);

回答2:

How about...

BigInteger bi = new BigInteger(my50DigitString);

All those Xxx.valueOf() methods are alternatives to constructors because they allow for returning shared, cached copies. Constructors, by definition, return a new instance every time. So valueOf() are a nice optimization, but the designers apparently didn't find it interesting to provide a BigInteger.valueOf(String) method. You'll have to use a one of the constructors in this case.

回答3:

BigInteger has a constructor that takes a String.

回答4:

Have you tried

BigInteger i = new BigInteger(s);

来源：https://stackoverflow.com/questions/1343982/biginteger-valueof-for-very-big-numbers