EqualsAndHashcode - Intellij Community

Reports classes that override the equals() method but do not override the hashCode() method or vice versa, which can potentially lead to problems when the class is added to a Collection or a HashMap.

The quick-fix generates the default implementation for an absent method.

Example:

class StringHolder {
  String s;

  @Override public int hashCode() {
    return s != null ? s.hashCode() : 0;
  }
}

After the quick-fix is applied:

class StringHolder {
  String s;

  @Override public int hashCode() {
    return s != null ? s.hashCode() : 0;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof StringHolder)) return false;

    StringHolder holder = (StringHolder)o;

    if (s != null ? !s.equals(holder.s) : holder.s != null) return false;

    return true;
  }
}