== Why is this an issue?

Generally it's not recommended to modify a collection while it's iterated and most JDK collection implementations don't support it. This may sometimes lead to a ConcurrentModificationException and it could be the source of incorrect or unspecified behaviors in the code.

This rule raises an issue when a method modifies the size of a collection, while the same collection is iterated.

=== Noncompliant code example

[source,java]
----
  public static void foo(List<String> lst) {
    for (String element : lst) {
      if (element.startsWith("x")) {
        lst.remove(element); // Noncompliant: lst size has been modified by "remove" call while it's iterated.
      }
    }
  }
----