binaryGCD

[shana07]

I have questions about binaryGCD from MutableBigInteger java core class and wish to confirm you guys. I have copied MutableBigInteger class into my folder. I need to write a MYPROGRAM to call bynaryGCD but I confuse about their modifiers...please advise. thanks a bunch
1.

class MutableBigInteger {  
//I ONLY can access this class from my main() when I put both 
classes (Mutable & MYPROGRAM) in a same package
 (because it's not public)? 

2.

MutableBigInteger hybridGCD(MutableBigInteger b) {
// This method calls binaryGCD below ...
 

3.

private MutableBigInteger binaryGCD(MutableBigInteger v) {
// Can I directly call this method without first call 
binaryGCD from MYPROGRAM?
 

4.

static int binaryGcd(int a, int b) {
// How about this one?can directly call this method too?
 

[shana07]

int a;
int y = BigInteger.trailingZeroTable[x];
a >>>= y;

Am I right by interpreting the 3rd line as shift 3 bit of int a to the right ..but what is y for? kindly share with me about this shift operation pls