using Float numbers for the map's key

Question

after I create a new object : Map<Float,Integer> m = new HashMap()<Float,Integer>;

I have an array with "float" numbers which are unique . I want to add these float numbers as the m's key! can I do this like : m.put(new Float(a[i]),"cat"); ?

thanks

Answer 1

I would recommend against using floating point numbers as hash map keys if possible. Your keys must match exactly when you look up values, and it's easy to get floating point numbers that aren't exactly right.

Answer 2

Just to take all answers together.

1. The mentioned Map cannot accept strings, so you cannot say m.put(f, "cat")
2. You can but do not have to wrap float using Float: auto-boxing does it for you automatically, so you can just say m.put(a[i],"cat")
3. You are not recommended to use floating point types (Float and Double) as map key. It may cause problems when you try to extract value from map using get(key) method
4. Note also that default type for floating constants is double, not float. So, be careful with floats, use them only if you really need them. In any case use float modifier near constants like 3.14f.