uint64_t_bigdec.java

import java.math.BigDecimal;

public class Main {

    public static void main(String[] args) {
        //0xFEDCBA9876543210
        BigDecimal dec = new BigDecimal("18364758544493064720");
        BigDecimal div = dec.divide(new BigDecimal("72057594037927936"));
        System.out.println("big decimal 2byte: " + Integer.toHexString(div.intValue()));

        long decLong = 0xFEDCBA9876543210L;
        System.out.println("long 2byte: " + Long.toHexString(decLong >>> 56));
    }
}