I want to know the number of bits really used in the long datatype in Java. 
For instance:

```
long time = System.currentTimeMillis();
System.out.println(java.lang.Long.toHexString(time));

```

Output:  

 12c95165393

Here you can see it only has 11 hex digits which means only 44 bits out of 64 are utilized. 10 bits are still un-utilized. Is there a way to know at runtime how many bits are used OR to pad the remaining bits ?