The ``++java.util.Collection++`` API has methods that accept ``++Object++`` parameters such as ``++Collection.remove(Object o)++``, and ``++Collection.contains(Object o)++``. When the actual type of the object provided to these methods is not consistent with the type declared on the ``++Collection++`` instantiation, those methods will always return ``++false++`` or ``++null++``. This is most likely unintended and hides a design problem.


This rule raises an issue when the type of the argument of the following APIs is unrelated to the type used for the ``++Collection++`` declaration:

* ``++Collection.remove(Object o)++``
* ``++Collection.removeAll(Collection<?>)++``
* ``++Collection.contains(Object o)++``
* ``++List.indexOf(Object o)++``
* ``++List.lastIndexOf(Object o)++``
* ``++Map.containsKey(Object key)++``
* ``++Map.containsValue(Object value)++``
* ``++Map.get(Object key)++``
* ``++Map.getOrDefault(Object key, V defaultValue)++``
* ``++Map.remove(Object key)++``
* ``++Map.remove(Object key, Object value)++``


== Noncompliant Code Example

----
public class S2175 {

  public static void main(String[] args) {
    String foo = "42";
    Map<Integer, Object> map = new HashMap<>();
    map.remove(foo); // Noncompliant; will return 'null' for sure because 'map' is handling only Integer keys

    // ...

    List<String> list = new ArrayList<String>();
    Integer integer = Integer.valueOf(1);
    if (list.contains(integer)) { // Noncompliant; always false.
      list.remove(integer); // Noncompliant; list.add(integer) doesn't compile, so this will always return 'false'
    }
  }

}
----


== See

* https://wiki.sei.cmu.edu/confluence/x/uDdGBQ[CERT, EXP04-J.] - Do not pass arguments to certain Java Collections Framework methods that are a different type than the collection parameter type


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