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I have a TreeMap with both values in BigDecimal, i'm trying to print some specific values so later i can do more complex operations, but i don't know which Map methods to use for BigDecimals, as the methods expect int values. This is my code :

R.S.
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  • Related: [Why Map.containsKey() takes an Object parameter instead of a speciallized type? [duplicate\]](https://stackoverflow.com/questions/8434153/why-map-containskey-takes-an-object-parameter-instead-of-a-speciallized-type) – Ole V.V. Feb 26 '19 at 14:36
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    It's not clear what you want to accomplish. The map does not contain the key 400 because that's an integer. It would be `map.containsKey(new BigDecimal(400))` – Michael Feb 26 '19 at 14:36
  • *as the methods expect int values* No they don’t. There’s no problem giving them a `BigInteger`. – Ole V.V. Feb 26 '19 at 14:37

2 Answers2

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Map methods expect Object or BigDecimal (depends on method). But int primitive type doesn't autoboxed to BigDecimal. You could create instance manually.

public class DemoApplication {

    public static void main(String[]args) {
        Map<BigDecimal, BigDecimal> map = new HashMap<>();
        // ...

        if (map.containsKey(BigDecimal.valueOf(400))) {
            System.out.println(map.keySet());
        }
    }

}
ilinykhma
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  • This prints `[400]`. Which just *might* explain the asker’s confusion. `400` *looks* like an `int`, but it really is a `BigInteger`. Or more precisely, the result of `toString` having been called implicitly on a `BigInteger`. – Ole V.V. Feb 26 '19 at 14:41
  • I can't use .put as the Map already has the keys and values set (as BigDecimals) and i cannot change them. I've tried just using BigDecimal.valueOf on containsKey but i get the following exception : java.lang.ClassCastException: java.math.BigDecimal cannot be cast to java.lang.Integer – R.S. Feb 26 '19 at 14:46
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    @ole-v-v The question is not clear. I think the problem was that the output of the author code is empty, but may be you are right. – ilinykhma Feb 26 '19 at 14:48
  • If you get ClassCastException, i think the value returned from getRowDTO.getMapSaldi() is not Map. Can you show listing or at least declaration of getMapSaldi()? – ilinykhma Feb 26 '19 at 14:52
  • Ok, this worked. The problem was the keySet method, i mistakenly thought i could use it to get the value, but i used map.get(BigDecimal.valueOf(400)) instead and it works as intended. Thank you. – R.S. Feb 26 '19 at 14:57
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Here is an example showing you how you can use a BigDecimal as a key for a map. I will be using a hashmap for this example.

Map<BigDecimal. BigDecimal> map = new HashMap<>();
//assuming this map has some values in it.
if(map.containsKey(new BigDecimal(400)){
    //do something
}
Bas van der Linden
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  • The map is already parametrized by the method tho', so it already contains keys and values of BigDecimal type. Wouldn't this just create a new BigDecimal that doesn't contain the value i need? – R.S. Feb 26 '19 at 14:50
  • @LordGriffith i just created the HashMap for demonstration perpouses, for you it would ofcouse be the map that you are using. – Bas van der Linden Feb 26 '19 at 14:53