How do I convert a String to a BigInteger?

java string biginteger
Twinone picture Twinone · Mar 30, 2013 · Viewed 198.6k times · Source

I'm trying to read some really big numbers from standard input and add them together.

However, to add to BigInteger, I need to use BigInteger.valueOf(long);:

private BigInteger sum = BigInteger.valueOf(0);

private void sum(String newNumber) {
    // BigInteger is immutable, reassign the variable:
    sum = sum.add(BigInteger.valueOf(Long.parseLong(newNumber)));
}

That works fine, but as the BigInteger.valueOf() only takes a long, I cannot add numbers greater than long's max value (9223372036854775807).

Whenever I try to add 9223372036854775808 or more, I get a NumberFormatException (which is completely expected).

Is there something like BigInteger.parseBigInteger(String)?

Answer

Uku Loskit picture Uku Loskit · Mar 30, 2013

Using the constructor

BigInteger(String val)

Translates the decimal String representation of a BigInteger into a BigInteger.

Javadoc

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