I came across two ways of getting BigDecimal object out of a double d.
Which would be a better approach? Would
valueOf create a new object?
In general (not just BigDecimal), what is recommended – new or valueOf?
Those are two separate questions: “What should I use for
BigDecimal?” and “What do I do in general?”
BigDecimal: this is a bit tricky, because they don’t do the same thing.
BigDecimal.valueOf(double) will use the canonical
String representation of the
double value passed in to instantiate the
BigDecimal object. In other words: The value of the
BigDecimal object will be what you see when you do
If you use
new BigDecimal(d) however, then the
BigDecimal will try to represent the
double value as accurately as possible. This will usually result in a lot more digits being stored than you want. Strictly speaking, it’s more correct than
valueOf(), but it’s a lot less intuitive.
There’s a nice explanation of this in the JavaDoc:
The results of this constructor can be somewhat unpredictable. One might assume that writing
new BigDecimal(0.1)in Java creates a
BigDecimalwhich is exactly equal to 0.1 (an unscaled value of 1, with a scale of 1), but it is actually equal to 0.1000000000000000055511151231257827021181583404541015625. This is because 0.1 cannot be represented exactly as a
double(or, for that matter, as a binary fraction of any finite length). Thus, the value that is being passed in to the constructor is not exactly equal to 0.1, appearances notwithstanding.
In general, if the result is the same (i.e. not in the case of
BigDecimal, but in most other cases), then
valueOf() should be preferred: it can do caching of common values (as seen on
Integer.valueOf()) and it can even change the caching behaviour without the caller having to be changed.
new will always instantiate a new value, even if not necessary (best example:
new Boolean(true) vs.