Chain of 'instanceof' checks

Reports any chains of if-else statements all of whose conditions are instanceof expressions or class equality expressions (e.g. comparison with String.class). Such constructions usually indicate a failure in object-oriented design which dictates that such type-based dispatch should be done via polymorphic method calls rather than explicit chains of type tests.

Example:

  double getArea(Shape shape) {
    // Warning: abstraction failure.
    // It would be better to declare a getArea()
    // abstract method in the shape interface
    // and implement it in every inheritor.
    if (shape instanceof Point) {
      return 0;
    }
    if (shape instanceof Circle) {
      return Math.PI *
        Math.pow(((Circle) shape).radius(), 2);
    }
    if (shape instanceof Rectangle) {
      return ((Rectangle) shape).width() *
        ((Rectangle) shape).height();
    }
    throw new IllegalArgumentException();
  }

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.

InstanceofChain

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 | Abstraction issues

Use the checkbox below to ignore instanceof expressions on library classes.

Inspection options

Here you can find the description of settings available for the Chain of 'instanceof' checks inspection, and the reference of their default values.

Ignore instanceof on library classes: Not selected

Availability

By default bundled with: IntelliJ IDEA 2024.1, Qodana for JVM 2024.1,
Can be installed with plugin: Java, 241.18072

Last modified: 18 June 2024