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Having an Interface provide an instance of a Class that implements it

1

If I have the interface:

public interface Val 
 public NilVal NIL;

And a singleton class that implements it:

public class NilVal implements Val 

 private static NilVal nil = null;

 private NilVal() 
 

 public static NilVal getInstance()
 if(nil == null)
 nil = new NilVal();
 return nil;
 

How would I go about instantiating NIL as a NilVal object in the interface?

java class interface singleton

share|improve this question

asked Mar 6 at 20:50

jipthechipjipthechip

84

add a comment | 

1

If I have the interface:

public interface Val 
 public NilVal NIL;

And a singleton class that implements it:

public class NilVal implements Val 

 private static NilVal nil = null;

 private NilVal() 
 

 public static NilVal getInstance()
 if(nil == null)
 nil = new NilVal();
 return nil;
 

How would I go about instantiating NIL as a NilVal object in the interface?

java class interface singleton

share|improve this question

asked Mar 6 at 20:50

jipthechipjipthechip

84

add a comment | 

If I have the interface:

public interface Val 
 public NilVal NIL;

And a singleton class that implements it:

public class NilVal implements Val 

 private static NilVal nil = null;

 private NilVal() 
 

 public static NilVal getInstance()
 if(nil == null)
 nil = new NilVal();
 return nil;
 

How would I go about instantiating NIL as a NilVal object in the interface?

java class interface singleton

share|improve this question

asked Mar 6 at 20:50

jipthechipjipthechip

84

public interface Val 
 public NilVal NIL;

public class NilVal implements Val 

 private static NilVal nil = null;

 private NilVal() 
 

 public static NilVal getInstance()
 if(nil == null)
 nil = new NilVal();
 return nil;
 

share|improve this question

asked Mar 6 at 20:50

jipthechipjipthechip

84

share|improve this question

asked Mar 6 at 20:50

jipthechipjipthechip

84

asked Mar 6 at 20:50

jipthechipjipthechip

84

asked Mar 6 at 20:50

jipthechipjipthechip

84

1 Answer
1

active

oldest

votes

1

You can do

public interface Val 
 Val NIL = NilVal.getInstance();

However you could also do

public interface Val 
 Val NIL = new NilVal();

 class NilVal implements Val 
 private NilVal() 
 

or even

public interface Val 
 Val NIL = NilVal.NIL;

 public enum NilVal implements Val NIL 

share|improve this answer

answered Mar 6 at 20:57

Peter LawreyPeter Lawrey

447k56573975

add a comment | 

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1

You can do

public interface Val 
 Val NIL = NilVal.getInstance();

However you could also do

public interface Val 
 Val NIL = new NilVal();

 class NilVal implements Val 
 private NilVal() 
 

or even

public interface Val 
 Val NIL = NilVal.NIL;

 public enum NilVal implements Val NIL 

share|improve this answer

answered Mar 6 at 20:57

Peter LawreyPeter Lawrey

447k56573975

add a comment | 

1

You can do

public interface Val 
 Val NIL = NilVal.getInstance();

However you could also do

public interface Val 
 Val NIL = new NilVal();

 class NilVal implements Val 
 private NilVal() 
 

or even

public interface Val 
 Val NIL = NilVal.NIL;

 public enum NilVal implements Val NIL 

share|improve this answer

answered Mar 6 at 20:57

Peter LawreyPeter Lawrey

447k56573975

add a comment | 

You can do

public interface Val 
 Val NIL = NilVal.getInstance();

However you could also do

public interface Val 
 Val NIL = new NilVal();

 class NilVal implements Val 
 private NilVal() 
 

or even

public interface Val 
 Val NIL = NilVal.NIL;

 public enum NilVal implements Val NIL 

share|improve this answer

answered Mar 6 at 20:57

Peter LawreyPeter Lawrey

447k56573975

public interface Val 
 Val NIL = NilVal.getInstance();

public interface Val 
 Val NIL = new NilVal();

 class NilVal implements Val 
 private NilVal() 
 

public interface Val 
 Val NIL = NilVal.NIL;

 public enum NilVal implements Val NIL 

share|improve this answer

answered Mar 6 at 20:57

Peter LawreyPeter Lawrey

447k56573975

answered Mar 6 at 20:57

Peter LawreyPeter Lawrey

447k56573975

answered Mar 6 at 20:57

Peter LawreyPeter Lawrey

447k56573975