Question 1: What is wrong with the following inteface:Answer 1:The documentation should reflect whypublic interface House { @Deprecated public void open(); public void openFrontDoor(); public void openBackDoor(); }open
is deprecated and what to use instead. For example:public interface House { /** * @deprecated use ofopen
is discouraged, use *openFrontDoor
oropenBackDoor
instead. */ @Deprecated public void open(); public void openFrontDoor(); public void openBackDoor(); }Question 2: Compile this program:
interface Closable { void close(); } class File implements Closable { @Override public void close() { //... close this file... } }What happens? Can you explain why?
Answer 2: The compiler generates an error complaining that
File.close
doesn't override any method from its superclass. This is because it is not overridingClosable.close
, it is implementing it!Question 3: Consider this implementation of the
House
interface, shown in Question 1.If you compile this program, the compiler complains thatpublic class MyHouse implements House { public void open() {} public void openFrontDoor() {} public void openBackDoor() {} }open
has been deprecated (in the interface). What can you do to get rid of that warning?Answer 3: You can deprecate the implementation of
open
:public class MyHouse implements House { //The documentation is inherited from the interface. @Deprecated public void open() {} public void openFrontDoor() {} public void openBackDoor() {} }Alternatively, you can suppress the warning:
public class MyHouse implements House { @SuppressWarnings("deprecation") public void open() {} public void openFrontDoor() {} public void openBackDoor() {} }