| Object.equals() contract states that "For any non-null reference value x, |
| x.equals(null) should return false". Thus all classes implementing equals() |
| function should gracefully handle null as an argument and return false. |
| Unfortunately, many classes throw NullPointerException when null is passed to |
| equals(). For example: |
| |
| ```java |
| @Override |
| public boolean equals(Object obj) { |
| if (!getClass().equals(obj.getClass())) { // NPE dereferencing obj |
| return false; |
| } |
| // … more member equality checking … |
| return true; |
| } |
| ``` |
| |
| EqualsBrokenForNull check modifies these equals() methods to add a null-check to |
| bring them into compliance for the equals() contract and avoid |
| NullPointerExceptions. |
| |
| ```java |
| @Override |
| public boolean equals(Object obj) { |
| if (obj == null) { |
| return false; |
| } |
| if (!getClass().equals(obj.getClass())) { |
| return false; |
| } |
| // … more member equality checking … |
| return true; |
| } |
| ``` |
