'equals()' and 'hashCode()' not paired

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;
  }
}

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

EqualsAndHashcode

Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | Java | Probable bugs

Inspection Details
By default bundled with:	IntelliJ IDEA 2024.3, Qodana for JVM 2024.3,
Can be installed with plugin:	Java, 243.23126

Last modified: 03 December 2024