Non-final field referenced in 'compareTo()'

Reports access to a non-final field inside a compareTo() implementation.

Such access may result in compareTo() returning different results at different points in the object's lifecycle, which may in turn cause problems when using the standard collections classes, for example java.util.TreeSet.

A quick-fix to make the field final is available only when there is no write access to the field, otherwise no fixes are suggested.

Example:

  class Foo implements Comparable<Foo>{
    private int index;
    Foo(int idx) {
      index = idx;
    }
    @Override
    public int compareTo(Foo foo) {
     return Integer.compare(this.index, foo.index);
    }
  }

After the quick-fix is applied:

  class Foo implements Comparable<Foo>{
    private final int index;
    Foo(int idx) {
      index = idx;
    }
    @Override
    public int compareTo(Foo foo) {
      return Integer.compare(this.index, foo.index);
    }
  }

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.

CompareToUsesNonFinalVariable

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 2024.2, Qodana for JVM 2024.2,
Can be installed with plugin:	Java, 242.22892

Last modified: 11 September 2024