How to add two java.lang.Numbers?

Question

I have two Numbers. Eg: ``` Number a = 2; Number b = 3; //Following is an error: Number c = a + b; ``` Why arithmetic operations are not supported on Numbers? Anyway how would I add these two numbers in java? (Of course I'm getting them from somewhere and I don't know if they are Integer or float etc).

Accepted Answer

You say you don't know if your numbers are integer or float... when you use the `Number` class, the compiler also doesn't know if your numbers are integers, floats or some other thing. As a result, the basic math operators like + and - don't work; the computer wouldn't know how to handle the values.

START EDIT

Based on the discussion, I thought an example might help. Computers store floating point numbers as two parts, a coefficient and an exponent. So, in a theoretical system, 001110 might be broken up as 0011 10, or 32 = 9. But positive integers store numbers as binary, so 001110 could also mean 2 + 4 + 8 = 14. When you use the class `Number`, you're telling the computer you don't know if the number is a float or an int or what, so it knows it has 001110 but it doesn't know if that means 9 or 14 or some other value.

END EDIT

What you can do is make a little assumption and convert to one of the types to do the math. So you could have

```
Number c = a.intValue() + b.intValue();
```

which you might as well turn into

```
Integer c = a.intValue() + b.intValue();
```

if you're willing to suffer some rounding error, or

```
Float c = a.floatValue() + b.floatValue();
```

if you suspect that you're not dealing with integers and are okay with possible minor precision issues. Or, if you'd rather take a small performance blow instead of that error,

```
BigDecimal c = new BigDecimal(a.floatValue()).add(new BigDecimal(b.floatValue()));
```

How to add two java.lang.Numbers?

Solution

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