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();
}

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

Inspection options

Option	Type	Default
Ignore instanceof on library classes	Checkbox	false

Inspection Details
Available in:	IntelliJ IDEA 2023.3, Qodana for JVM 2023.3
Plugin:	Java, 233.SNAPSHOT

Last modified: 13 July 2023