Multiple inheritance for an anonymous class

Question

How can an anonymous class implement two  or more  interfaces  Alternatively  how can it both extend a class and implement an interface  For example  I want to create an object of anonymous class that extends two interfaces         Java 10  quot var quot  is used since I don t know how to specify its type     var lazilyInitializedFileNameSupplier    new Supplier lt String gt  implements AutoCloseable              private String generatedFileName           Override         public String get        Generate file only once             if  generatedFileName    null                  generatedFileName   generateFile                              return generatedFileName                     Override         public void close   throws Exception      Clean up             if  generatedFileName    null                     Delete the file if it was generated               generatedFileName   null                                  Then I can use it in a try-with-resources block as AutoCloseable as lazily-initialized utility class          try  lazilyInitializedFileNameSupplier                   Some complex logic that might or might not                 invoke the code that creates the file             if  checkIfNeedToProcessFile                      doSomething lazilyInitializedFileNameSupplier get                               if  checkIfStillNeedFile                      doSomethingElse lazilyInitializedFileNameSupplier get                                         By now we are sure that even if the file was generated  it doesn t exist anymore  I don t want to create an inner class because I m absolutely sure that this class won t be used anywhere except the method I need to use it in  and I also might want to use local variables declared in that method that might be of var type

User · Answer

An anonymous class is extending or implementing while creating its object For example :

Interface in = new InterFace()
{

..............

}

Here anonymous class is implementing Interface.

Class cl = new Class(){

.................

}

here anonymous Class is extending a abstract Class.

User · Answer

I guess nobody understood the question  I guess what this guy wanted was something like this   return new  class implements MyInterface        Override     public void myInterfaceMethod       do something           because this would allow things like multiple interface implementations   return new  class implements MyInterface  AnotherInterface        Override     public void myInterfaceMethod       do something           Override     public void anotherInterfaceMethod       do something           this would be really nice indeed  but that s not allowed in Java   What you can do is use local classes inside method blocks   public AnotherInterface createAnotherInterface         class LocalClass implements MyInterface  AnotherInterface            Override         public void myInterfaceMethod       do something               Override         public void anotherInterfaceMethod       do something               return new LocalClass

User · Answer

The interface interface Blah       void something               Something that expects an object implementing that interface void chewOnIt Blah b        b something               Let s provide an object of an anonymous class chewOnIt      new Blah              Override         void something     System out println  Anonymous something

User · Answer

Anonymous classes always extend superclass or implements interfaces  for example   button addActionListener new ActionListener       ActionListener is an interface     public void actionPerformed ActionEvent e               Moreover  although anonymous class cannot implement multiple interfaces  you can create an interface that extends other interface and let your anonymous class to implement it

User · Answer

An anonymous class usually implements an interface   new Runnable        implements Runnable     public void run         JFrame addWindowListener  new WindowAdapter        extends  class        If you mean whether you can implement 2 or more interfaces  than I think that s not possible  You can then make a private interface which combines the two  Though I cannot easily imagine why you would want an anonymous class to have that    public class MyClass      private interface MyInterface extends Runnable  WindowListener             Runnable r   new MyInterface            your anonymous class which implements 2 interaces

User · Answer

Anonymous classes must extend or implement something  like any other Java class  even if it s just java lang Object   For example   Runnable r   new Runnable        public void run                Here  r is an object of an anonymous class which implements Runnable   An anonymous class can extend another class using the same syntax   SomeClass x   new SomeClass                 What you can t do is implement more than one interface  You need a named class to do that  Neither an anonymous inner class  nor a named class  however  can extend more than one class

[java] Multiple inheritance for an anonymous class

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