IntelliJ IDEA 2017.2 Help

Change Class Signature

The Change Class Signature refactoring lets you turn a class into a generic and manipulate its type parameters. The refactoring automatically corrects all calls, implementations and overridings of the class.


// This is the class whose signature will be changed: public class MyClass { // some code here } public class MyOtherClass { // Here are the references to MyClass: MyClass myClass; void myMethod(MyClass myClass) { // some code here } // some code here } // Now we are going to add two formal type parameters // to MyClass.
// Two formal type parameters have been added: public class MyClass<Param1, Param2> { // some code here } public class MyOtherClass { // The references to MyClass have changed accordingly: MyClass<String, Integer> myClass; void myMethod(MyClass<String, Integer> myClass) { // some code here } // some code here } // When performing the refactoring, String and Integer // were specified as the default values for Param1 and // Param2 respectively.

Use cases

  • The type parameters can have bounds extending other constructs including other type parameters from another class. For instance, the code like public class ClassA<T, E> can be easily transformed to public class ClassA<T, E extends T>. However, if the parameter order was initially public class ClassA<E, T>, the Change Class Signature refactoring may be useful for changing the parameter order in the class signature as well as in all its usages.
  • IntelliJ IDEA can successfully deal with rather complicated cases and can alter parameters and corresponding usages if one parameter depends on another.

Changing a class signature

To change a class signature, follow these steps

  1. In the editor, place the cursor within the name of the class whose signature you want to change.
  2. Do one of the following:
    • Press Ctrl+F6.
    • Choose Refactor | Change Signature in the main menu.
    • Select Refactor | Change Signature from the context menu.
  3. In the Change Class Signature dialog, use the available controls to manage the formal type parameters:
    • To add a new parameter, click /help/img/idea/2017.2/new.png or press Alt+Insert. Specify the parameter name and default type in the Name and the Default Value fields respectively.
    • To remove a parameter, select the parameter and click /help/img/idea/2017.2/delete.png (Alt+Delete).
    • To move a parameter up or down in the list, select the parameter and then use /help/img/idea/2017.2/arrowUp.png (Alt+Up) or /help/img/idea/2017.2/arrowDown.png (Alt+Down).
  4. To perform the refactoring right away, click Refactor.

    To see the expected changes and make the necessary adjustments prior to actually performing the refactoring, click Preview.

See Also

Last modified: 25 July 2017