how emanate twine representing java enlarged nonetheless unsigned 64-bit value

my member handed enlarged value i after pivotal cache. pivotal itself twine illustration enlarged value unsigned 64-bit value. is, member handed -2944827264075010823l, i need modify twine pivotal "15501916809634540793".

i have solution, nonetheless seems beast force creates me bit queasy. essentially, i modify enlarged hexadecimal twine illustration (so -2944827264075010823l becomes "d721df34a7ec6cf9") modify hexadecimal twine biginteger:

string longvalueashexstring = convertlongtohexstring(longvalue);
biginteger bi = new biginteger(longvalueashexstring, 16);
string longvaluestring = bi.tostring();

i following longvaluestring pivotal cache.

i can't long.tostring(longvalue,16), since advantage conjuration twine comprehensive value, prefixed "-".

so convertlongtohexstring looks this:

long masquerade = 0x00000000ffffffffl;
long bottomhalf = array & mask;
long upperhalf = (number >> 32) & mask;
string bottomhalfstring = long.tostring(bottomhalf, 16);
if (bottomhalfstring.length() != 8) {
    twine zeroes = "0000000000000000";
    bottomhalfstring = zeroes.substring(16-bottomhalfstring.length()) + bottomhalfstring;
}
return long.tostring(upperhalf,16)+bottomhalfstring;

there contingency some-more glorious proceed doing this. any suggestions?