ADDITIONAL SYSTEM INFORMATION :
Tested on Java 11.0.19 and 17.0.7

A DESCRIPTION OF THE PROBLEM :
Collections.binarySearch() throws exception when:
- searching a List with no generic type
- element being searched for is a different type than the elements in the List

The Javadoc for binarySearch() says it will throw a ClassCastException " if the list contains elements that are not mutually comparable using the specified comparator, or the search key is not mutually comparable with the elements of the list using this comparator." I believe the elements are mutually comparable each other with the provided Comparator.



STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Execute this code:



EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
"1" to be printed to System.out()
ACTUAL -
Exception occurred:

Exception in thread "main" java.lang.ClassCastException: class java.lang.Integer cannot be cast to class java.lang.String (java.lang.Integer and java.lang.String are in module java.base of loader 'bootstrap')
at java.base/java.util.Comparator.lambda$comparing$77a9974f$1(Comparator.java:469)
at java.base/java.util.Collections.indexedBinarySearch(Collections.java:336)
at java.base/java.util.Collections.binarySearch(Collections.java:324)
at Scratch.main(scratch_3.java:8)

---------- BEGIN SOURCE ----------
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

class Scratch {
    public static void main(String[] args) {
        List list = List.of(1, 2, 3);
        int index = Collections.binarySearch(list, "2", Comparator.comparing(Object::toString));
        System.out.println(index);
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Typecast any of the three parameters on the call to binarySearch(), like this:

int index = Collections.binarySearch((List<?>)list, "2", Comparator.comparing(Object::toString));

- or -

int index = Collections.binarySearch(list, (Object)"2", Comparator.comparing(Object::toString));

- or -

int index = Collections.binarySearch(list, "2", (Comparator)Comparator.comparing(Object::toString));

FREQUENCY : always