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

User · Accepted Answer

Using the constructor      BigInteger String val       Translates the decimal String representation of a BigInteger into a BigInteger    Javadoc

User · Answer

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

User · Answer

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 lt n  i         series i    new BigInteger unsorted i      convert String to bigInteger

User · Answer

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

User · Answer

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

User · Answer

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

[java] How do I convert a String to a BigInteger?

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