Unreachable code

Reports the code which is never reached according to data flow analysis. It can be the result of previous always-true or always-false condition, unreachable loop body or catch section. Usually (though not always) unreachable code is a consequence of a previous warning, so check inspection warnings form "Nullability and data flow problems", "Constant values", or "Redundant operation on empty container" to better understand the cause.

Example:

  void finishApplication() {
    System.exit(0);
    System.out.println("Application is terminated"); // Unreachable code
  }

Note that this inspection relies on method contract inference. In particular, if you call a static or final method that always throws an exception, then the "always failing" contract will be inferred, and code after the method call will be considered unreachable. For example:

  void run() {
    performAction();
    System.out.println("Action is performed"); // Unreachable code
  }
  
  static void performAction() {
    throw new AssertionError();
  }

This may cause false-positives if any kind of code postprocessing is used, for example, if an annotation processor later replaces the method body with something useful. To avoid false-positive warnings, one may suppress the automatic contract inference with explicit @org.jetbrains.annotations.Contract annotation from org.jetbrains:annotations package:

  void run() {
    performAction();
    System.out.println("Action is performed"); // No warning anymore
  }

  @Contract("-> _") // implementation will be replaced
  static void performAction() {
    throw new AssertionError();
  }

New in 2024.1

Inspection options

Here you can find the description of settings available for the Unreachable code inspection, and the reference of their default values.

Ignore trivial exit statements: Default: Selected
Respect 'Constant value' inspection suppressions: Default: Selected

Inspection Details
By default bundled with:	IntelliJ IDEA 2024.1, Qodana for JVM 2024.1,
Can be installed with plugin:	Java, 241.16690

Last modified: 29 April 2024