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);:

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)?

Joachim Sauer · Accepted Answer · 2023-04-26 10:22:30Z

166

Using the constructor

public BigInteger(String val)

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

Javadoc

edited Apr 26, 2023 at 10:22

Joachim Sauer

309k59 gold badges568 silver badges624 bronze badges

answered Mar 30, 2013 at 10:03

Uku Loskit

42.2k9 gold badges97 silver badges98 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Arun Over a year ago

I tried the same but faced issue coz i missed to import java.math.BigInteger

pdem Over a year ago

ok, from integer: valueOf, from String, constructor, this API miss some coherence?

Community · Accepted Answer · 2020-06-20 09:12:55Z

30

According to the documentation:

BigInteger(String val)

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

It means that you can use a String to initialize a BigInteger object, as shown in the following snippet:

sum = sum.add(new BigInteger(newNumber));

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Mar 30, 2013 at 10:07

Vito Gentile

14.7k11 gold badges65 silver badges99 bronze badges

Comments

Rudy Velthuis · Accepted Answer · 2016-07-01 14:49:40Z

10

Instead of using valueOf(long) and parse(), you can directly use the BigInteger constructor that takes a string argument:

BigInteger numBig = new BigInteger("8599825996872482982482982252524684268426846846846846849848418418414141841841984219848941984218942894298421984286289228927948728929829");

That should give you the desired value.

edited Jul 1, 2016 at 14:49

Rudy Velthuis

28.9k5 gold badges50 silver badges97 bronze badges

answered Jul 1, 2016 at 11:55

User9123

1011 silver badge3 bronze badges

Comments

fl0w · Accepted Answer · 2019-07-18 13:44:25Z

10

BigInteger has a constructor where you can pass string as an argument.

try below,

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

edited Jul 18, 2019 at 13:44

fl0w

3,94534 silver badges38 bronze badges

answered Mar 30, 2013 at 10:12

Darshit Chokshi

5893 silver badges13 bronze badges

Comments

Omar Mohammed · Accepted Answer · 2017-10-01 02:56:40Z

2

For a loop where you want to convert an array of strings to an array of bigIntegers do this:

String[] unsorted = new String[n]; //array of Strings
BigInteger[] series = new BigInteger[n]; //array of BigIntegers

for(int i=0; i<n; i++){
    series[i] = new BigInteger(unsorted[i]); //convert String to bigInteger
}

edited Oct 1, 2017 at 2:56

user4447799

answered Oct 1, 2017 at 2:47

Omar Mohammed

214 bronze badges

Comments

Bhargav Rao · Accepted Answer · 2020-04-15 15:38:48Z

0

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;
}

edited Apr 15, 2020 at 15:38

Bhargav Rao

52.6k29 gold badges130 silver badges142 bronze badges

answered Apr 15, 2020 at 12:57

Aaron

12 bronze badges

Collectives™ on Stack Overflow

How do I convert a String to a BigInteger?

6 Answers 6

2 Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

2 Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related