Review

Checks the return value of Map.put() to check whether the key was set before. If the Map allows null values, this usage breaks.

Use Map.containsKey() to check whether a key is set.

• missing/condition/value_or_state

mubench/examples/survey/Maps.java

mapMayContainNull(Map)

class Maps {
	void mapMayContainNull(Map<String, Object> m) {
		if (m.put("foo", new Object()) != null) {
			// "foo" was set before
		} else {
			// "foo" was not set before (or set to null!)
		}
	}

}

public class Contains {
  public void pattern(Map<String, Object> m, String key, Object value) {
    if (m.containsKey(key)) {
      // key was set before
    } else {
      // key was not set before
      m.put(key, value);
    }
  }
}