## Why is this an issue?

Passing a collection as an argument to the collection’s own method is either an error - some other argument was intended - or simply nonsensical code.

Further, because some methods require that the argument remain unmodified during the execution, passing a collection to itself can result in undefined behavior.

### Noncompliant code example

    List <Object> objs = new ArrayList<Object>();
    objs.add("Hello");

    objs.add(objs); // Noncompliant; StackOverflowException if objs.hashCode() called
    objs.addAll(objs); // Noncompliant; behavior undefined
    objs.containsAll(objs); // Noncompliant; always true
    objs.removeAll(objs); // Noncompliant; confusing. Use clear() instead
    objs.retainAll(objs); // Noncompliant; NOOP