Java Utililty Methods BigInteger Reverse

String num = currentSum.toString();
String rev = new StringBuilder(num).reverse().toString();
BigInteger revNum = new BigInteger(rev);
return revNum;

String s = n.toString();
StringBuilder sb = new StringBuilder(s);
return new BigInteger(sb.reverse().toString());

try {
 if (width < Long.SIZE)
 return BigInteger.valueOf(reverse(x.longValueExact(), width));
} catch (ArithmeticException ex) {
StringBuilder str = new StringBuilder(x.toString(2));
if (str.length() > width)
 str.delete(0, str.length() - width);
...