Conversion to and from BigInteger

import java.math.BigInteger;
import java.util.Arrays;

public class BigIntegerConversion {
    public static void main(String[] args) {

        // Conversion to BigInteger

        // From int
        int intVal = 1000;
        BigInteger fromInt = BigInteger.valueOf(intVal);

        // From long
        long longVal = 9876543210L;
        BigInteger fromLong = BigInteger.valueOf(longVal);

        // From decimal string
        String decimalString = "12345678901234567890";
        BigInteger fromDecimalString = new BigInteger(decimalString);

        // From binary string
        String binaryString = "1010101010";
        BigInteger fromBinaryString = new BigInteger(binaryString, 2);

        // From hex string
        String hexString = "1F4A9";
        BigInteger fromHexString = new BigInteger(hexString, 16);

        // From byte array
        byte[] byteArray = {0x01, 0x02, 0x03};  // equivalent to 66051
        BigInteger fromBytes = new BigInteger(byteArray);

        // Conversion from BigInteger

        int backToInt = fromInt.intValue();
        long backToLong = fromLong.longValue();
        double backToDouble = fromDecimalString.doubleValue();

        String backToString = fromDecimalString.toString(); // decimal string
        String backToBinary = fromBinaryString.toString(2); // binary string
        String backToHex = fromHexString.toString(16);      // hex string

        byte[] backToByteArray = fromHexString.toByteArray();

        // Output
        System.out.println("---- Conversion TO BigInteger ----");
        System.out.println("From int: " + fromInt);
        System.out.println("From long: " + fromLong);
        System.out.println("From decimal string: " + fromDecimalString);
        System.out.println("From binary string: " + fromBinaryString);
        System.out.println("From hex string: " + fromHexString);
        System.out.println("From byte array: " + fromBytes);

        System.out.println("\n---- Conversion FROM BigInteger ----");
        System.out.println("To int: " + backToInt);
        System.out.println("To long: " + backToLong);
        System.out.println("To double: " + backToDouble);
        System.out.println("To string (decimal): " + backToString);
        System.out.println("To string (binary): " + backToBinary);
        System.out.println("To string (hex): " + backToHex);
        System.out.println("To byte array: " + Arrays.toString(backToByteArray));
    }
}