Arguments to collection remove* methods must be of the same type as the collection itself.

Though Collection is parameterised on the type of the contained values, Collection.remove() is not; it accepts a parameter of type Object instead. This means any value can be passed to a collection's remove() method, regardless of whether the value's type matches the collection's type.

This is also exacerbated for lists that store integers; List has both an Object and an int overload for remove() that are easy to confuse.

Bad Practice

List<Integer> ints = Arrays.asList(3);

ints.remove("3"); // this will fail silently!

Recommended

Ensure that the type of the value passed to remove() is the same as the collection's type.

ints.remove((Object)3);

References

• Oracle Java 11 JavaDocs - java.util.Collection