infer_clone/infer/documentation/issues/INEFFICIENT_KEYSET_ITERATOR.md

This issue is raised when

• iterating over a HashMap with ketSet() iterator
• looking up the key each time

Instead, it is more efficient to iterate over the loop with entrySet which returns key-vaue pairs and gets rid of the hashMap lookup. For instance, we would raise an issue for the following program:

void inefficient_loop_bad(HashMap<String, Integer> testMap) {
 for (String key : testMap.keySet()) {
   Integer value = testMap.get(key); // extra look-up cost
   foo(key, value);
 }
}

Instead, it is more efficient to have:

void efficient_loop_ok(HashMap<String, Integer> testMap) {
  for (Map.Entry<String, Integer> entry : testMap.entrySet()) {
    String key = entry.getKey();
    Integer value = entry.getValue();
    foo(key, value);
  }
}