Setting map value with Long key

[mevlana14]

Hello there, while using the following scenario, I am getting an unexpected output (which is unexpected with my current understanding). Is this normal behavior?

edit: version: 5.0.2

import org.instancio.Instancio;

import java.util.List;
import java.util.Map;
import java.util.TreeMap;

import static org.instancio.Select.field;

class Scratch {
    public static void main(String[] args) {
        Foo foo = Instancio.of(Foo.class)
                .set(field(Foo::bar), new TreeMap<>(
                                Map.of(
                                        0,
                                        List.of(
                                                List.of(1, 1, 3, 5),
                                                List.of(1, 2, 3, 5),
                                                List.of(2, 2, 3, 5),
                                                List.of(2, 3, 4, 5),
                                                List.of(3, 3, 4, 5),
                                                List.of(3, 4, 5, 5)
                                        )
                                )
                        )
                )
                .create();
    }

    record Foo(TreeMap<Long, List<List<Integer>>> bar) {
    }
}

This call foo.bar().get(0L) results in a compile error because the class java.lang.Integer cannot be cast to class java.lang.Long. However, two assignments below are able to assign a TreeMap<Integer, List<List<Integer>>> instance to Foo.bar.

Map<Long, List<List<Integer>>> zzz = Map.of(
      0,
      List.of(
              List.of(1, 1, 3, 5),
              List.of(1, 2, 3, 5),
              List.of(2, 2, 3, 5),
              List.of(2, 3, 4, 5),
              List.of(3, 3, 4, 5),
              List.of(3, 4, 5, 5)
      )
);

TreeMap<Long, List<List<Integer>>> sss = new TreeMap<>(
      Map.of(
              0,
              List.of(
                      List.of(1, 1, 3, 5),
                      List.of(1, 2, 3, 5),
                      List.of(2, 2, 3, 5),
                      List.of(2, 3, 4, 5),
                      List.of(3, 3, 4, 5),
                      List.of(3, 4, 5, 5)
              )
      )
);

thank you!

[armandino]

Hi @mevlana14! Firstly, I wanted to thank you for supporting Instancio! ❤️

Regarding the error, this is caused by the primitive 0 in Map.of(0, ...) being converted to an Integer. Since Instancio's set() method accepts any object, there's no type information available to the compiler to give you an error. As a result, the field gets assigned:

TreeMap<Integer, List<List<Integer>>>

instead of

TreeMap<Long, List<List<Integer>>>

To fix it, you can specify the numeric type explicitly:

Foo foo = Instancio.of(Foo.class)
                .set(field(Foo::bar), new TreeMap<>(
                                Map.of(
                                        0L,  // 0L instead of 0
                                        List.of(
                                                List.of(1, 1, 3, 5),
                                                List.of(1, 2, 3, 5),
                                                List.of(2, 2, 3, 5),
                                                List.of(2, 3, 4, 5),
                                                List.of(3, 3, 4, 5),
                                                List.of(3, 4, 5, 5)
                                        )
                                )
                        )
                )
                .create();

This should resolve the class cast error.

[mevlana14]

❤️ you are welcome!
Following code does not generate foo since int 10 can not be assigned to long field. I was expecting a similar output with this code, but while debugging, I noticed that key-value types are ignored when generating collections and and it’s all about the Java lang itself, not the Instancio.

import org.instancio.Instancio;

import static org.instancio.Select.field;

class Scratch {
    public static void main(String[] args) {
        Foo foo = Instancio.of(Foo.class)
                .set(field(Foo::zzz), 10)
                .create();
    }

    record Foo(Long zzz) {
    }
}

thanks for suggestion! 🙂

[armandino]

Ah yes, there's some validation when assigning values, but this doesn't check nested object properties or collection elements. That's why it fell through the cracks :)