Here you can find the source of convertPositive(BigInteger bi)
public static BigInteger convertPositive(BigInteger bi)
//package com.java2s; //License from project: Apache License import java.math.BigInteger; public class Main { public static BigInteger convertPositive(BigInteger bi) { if (bi.signum() < 0) { bi = new BigInteger(1, bi.toByteArray()); }//from w w w.j a va 2 s. com return bi; } }