IntelliJ IDEA 2018.2 Help

Use Interface Where Possible

Use Interface Where Possible refactoring delegates execution of the specified methods, derived from a base class/interface, to an instance of an ancestor class or an inner class, implementing the same interface.

  1. In the editor, place the caret at a class which methods should be delegated to its parent class or interface.
  2. On the main menu or on the context menu, select Refactor | Use Interface Where Possible.
  3. In the dialog that opens, select the parent object that will replace the usages of the current class.
  4. To replace the current class name in instanceof statements, check the option Use interface/superclass in instanceof.

    Note that if you use instanceof statements and leave this checkbox unselected, you may receive erroneous code, such as:

    if (secondInterface instanceof Class)

    This code will compile, but may produce undesired results.

  5. Preview and apply the changes.

Example

BeforeAfter
// File Class.java public class Class implements Interface { public void publicMethod() { ... } public void hiddenMethod() { ... } }
// File Class.java UNCHANGED public class Class implements Interface { public void publicMethod() { ... } public void hiddenMethod() { ... } }
// File Interface.java public interface Interface { int CONSTANT=0; void publicMethod(); }
// File Interface.java UNCHANGED public interface Interface { int CONSTANT=0; void publicMethod(); }
// File AnotherClass.java public class AnotherClass { Class firstClass; Class secondClass; public void method() { firstClass.publicMethod(); firstClass.hiddenMethod(); secondClass.publicMethod(); if (secondClass instanceof Class) { ... } ... } }
// File AnotherClass.java MODIFIED public class AnotherClass { Class firstClass; Interface secondInterface; public void method() { firstClass.publicMethod(); firstClass.hiddenMethod(); secondInterface.publicMethod(); if (secondInterface instanceof Interface) { ... } ... } }
Last modified: 18 June 2018

See Also