How do I convert a String to a BigInteger?

Question

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);

Answer 1

If you may want to convert plaintext (not just numbers) to a BigInteger you will run into an exception, if you just try to: new BigInteger("not a Number")

In this case you could do it like this way:

public  BigInteger stringToBigInteger(String string){
    byte[] asciiCharacters = string.getBytes(StandardCharsets.US_ASCII);
    StringBuilder asciiString = new StringBuilder();
    for(byte asciiCharacter:asciiCharacters){
        asciiString.append(Byte.toString(asciiCharacter));
    }
    BigInteger bigInteger = new BigInteger(asciiString.toString());
    return bigInteger;
}