One might assume that "new BigDecimal(.1)" is exactly equal
to .1, but it is actually equal
to .1000000000000000055511151231257827021181583404541015625.
This is so because .1 cannot be represented exactly as a double
(or, for that matter, as a binary fraction of any finite length).
Thus, the long value that is being passed in to the constructor
is not exactly equal to .1, appearances notwithstanding.
The (String) constructor, on the other hand, is perfectly predictable:
'new BigDecimal(".1")' is exactly equal to .1, as one
would expect. Therefore, it is generally recommended that the (String)
constructor be used in preference to this one.import java.math.BigDecimal;
public class Test {
public static void main(String[] args) {
// this would trigger the rule
BigDecimal bd=new BigDecimal(1.123);
// this wouldn't trigger the rule
BigDecimal bd=new BigDecimal("1.123");
// this wouldn't trigger the rule
BigDecimal bd=new BigDecimal(12);
}
}
