Casting an instance of Object to primitive type or Object Type

Question

when I need to cast an instance of type `Object` to a double , which of the following is better and why ? `Double d = (Double) object;` Or `double d = (double) object;`

Accepted Answer

The difference is that the first form will succeed if `object` is null - the second will throw a `NullPointerException`. So if it's valid for `object` to be null, use the first - if that indicates an error condition, use the second.

This:

```
double d = (double) object;
```

is equivalent to:

```
Double tmp = (Double) object;
double t = tmp.doubleValue();
```

(Or just `((Double)object).doubleValue()` but I like separating the two operations for clarity.)

Note that the cast to `double` is only valid under Java 7 - although it's not clear from the Java 7 language enhancements page why that's true.

Casting an instance of Object to primitive type or Object Type

Solution

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