can we make use of polymorphism by inheriting an empty class?
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I want to use Generics concept and create an ArrayList that needs to take different types of objects so I want to create an empty class called ObjectType and inherit it via 'Person and Animal' classes and want to create ArrayList as below
List<? extends ObjectType> list=new ArrayList<Persons>();
but it is not working what is the solution?
java
edited Nov 11 at 13:15
Gihan Saranga Siriwardhana
613217
asked Nov 11 at 12:31
Nagendhra Kumar Sunkara
1
add a comment |
up vote
-2
down vote
favorite
I want to use Generics concept and create an ArrayList that needs to take different types of objects so I want to create an empty class called ObjectType and inherit it via 'Person and Animal' classes and want to create ArrayList as below
List<? extends ObjectType> list=new ArrayList<Persons>();
but it is not working what is the solution?
java
edited Nov 11 at 13:15
Gihan Saranga Siriwardhana
613217
asked Nov 11 at 12:31
Nagendhra Kumar Sunkara
1
Can you mention your class implementation?
– GauravRai1512
Nov 11 at 12:33
public class ObjectType(){ public class Person extends ObjectType(){ public name,location,id,salary; //followed by a constructor for initialisation } then want to add perosn objects to arraylist as below List<? extends ObjectType> list=new ArrayList<Person>();
– Nagendhra Kumar Sunkara
Nov 11 at 12:35
If you are creating empty class then i would suggest to use interface rather then class and implement your animal and person class.
– GauravRai1512
Nov 11 at 12:37
There is one correction public class ObjectType{} rather then public class ObjectType(){}
– GauravRai1512
Nov 11 at 12:43
1
Don't put more information into comments, always update your question instead. Or can you really read that code only comments you made?
– GhostCat
Nov 11 at 12:45
add a comment |
up vote
-2
down vote
favorite
up vote
-2
down vote
favorite
I want to use Generics concept and create an ArrayList that needs to take different types of objects so I want to create an empty class called ObjectType and inherit it via 'Person and Animal' classes and want to create ArrayList as below
List<? extends ObjectType> list=new ArrayList<Persons>();
but it is not working what is the solution?
java
edited Nov 11 at 13:15
Gihan Saranga Siriwardhana
613217
asked Nov 11 at 12:31
Nagendhra Kumar Sunkara
1
I want to use Generics concept and create an ArrayList that needs to take different types of objects so I want to create an empty class called ObjectType and inherit it via 'Person and Animal' classes and want to create ArrayList as below
List<? extends ObjectType> list=new ArrayList<Persons>();
but it is not working what is the solution?
java
java
edited Nov 11 at 13:15
Gihan Saranga Siriwardhana
613217
asked Nov 11 at 12:31
Nagendhra Kumar Sunkara
1
edited Nov 11 at 13:15
Gihan Saranga Siriwardhana
613217
asked Nov 11 at 12:31
Nagendhra Kumar Sunkara
1
edited Nov 11 at 13:15
Gihan Saranga Siriwardhana
613217
edited Nov 11 at 13:15
Gihan Saranga Siriwardhana
613217
edited Nov 11 at 13:15
Gihan Saranga Siriwardhana
613217
613217
asked Nov 11 at 12:31
Nagendhra Kumar Sunkara
1
asked Nov 11 at 12:31
Nagendhra Kumar Sunkara
1
asked Nov 11 at 12:31
Nagendhra Kumar Sunkara
1
1
Can you mention your class implementation?
– GauravRai1512
Nov 11 at 12:33
public class ObjectType(){ public class Person extends ObjectType(){ public name,location,id,salary; //followed by a constructor for initialisation } then want to add perosn objects to arraylist as below List<? extends ObjectType> list=new ArrayList<Person>();
– Nagendhra Kumar Sunkara
Nov 11 at 12:35
If you are creating empty class then i would suggest to use interface rather then class and implement your animal and person class.
– GauravRai1512
Nov 11 at 12:37
There is one correction public class ObjectType{} rather then public class ObjectType(){}
– GauravRai1512
Nov 11 at 12:43
1
Don't put more information into comments, always update your question instead. Or can you really read that code only comments you made?
– GhostCat
Nov 11 at 12:45
add a comment |
Can you mention your class implementation?
– GauravRai1512
Nov 11 at 12:33
public class ObjectType(){ public class Person extends ObjectType(){ public name,location,id,salary; //followed by a constructor for initialisation } then want to add perosn objects to arraylist as below List<? extends ObjectType> list=new ArrayList<Person>();
– Nagendhra Kumar Sunkara
Nov 11 at 12:35
If you are creating empty class then i would suggest to use interface rather then class and implement your animal and person class.
– GauravRai1512
Nov 11 at 12:37
There is one correction public class ObjectType{} rather then public class ObjectType(){}
– GauravRai1512
Nov 11 at 12:43
1
Don't put more information into comments, always update your question instead. Or can you really read that code only comments you made?
– GhostCat
Nov 11 at 12:45
Can you mention your class implementation?
– GauravRai1512
Nov 11 at 12:33
Can you mention your class implementation?
– GauravRai1512
Nov 11 at 12:33
public class ObjectType(){ public class Person extends ObjectType(){ public name,location,id,salary; //followed by a constructor for initialisation } then want to add perosn objects to arraylist as below List<? extends ObjectType> list=new ArrayList<Person>();
– Nagendhra Kumar Sunkara
Nov 11 at 12:35
public class ObjectType(){ public class Person extends ObjectType(){ public name,location,id,salary; //followed by a constructor for initialisation } then want to add perosn objects to arraylist as below List<? extends ObjectType> list=new ArrayList<Person>();
– Nagendhra Kumar Sunkara
Nov 11 at 12:35
If you are creating empty class then i would suggest to use interface rather then class and implement your animal and person class.
– GauravRai1512
Nov 11 at 12:37
If you are creating empty class then i would suggest to use interface rather then class and implement your animal and person class.
– GauravRai1512
Nov 11 at 12:37
There is one correction public class ObjectType{} rather then public class ObjectType(){}
– GauravRai1512
Nov 11 at 12:43
There is one correction public class ObjectType{} rather then public class ObjectType(){}
– GauravRai1512
Nov 11 at 12:43
1
1
Don't put more information into comments, always update your question instead. Or can you really read that code only comments you made?
– GhostCat
Nov 11 at 12:45
Don't put more information into comments, always update your question instead. Or can you really read that code only comments you made?
– GhostCat
Nov 11 at 12:45
add a comment |
1 Answer
1
active
oldest
votes
up vote
0
down vote
In general, I would use an interface rather than a class wherever possible as it is simpler and more flexible.
What you can write is
interface ObjectType { }
class Animal implements ObjectType { }
class Person implements ObjectType { }
List<ObjectType> objects = new ArrayList<>();
This might not do what you expect, however how you solve this depends on what you need the List to do.
answered Nov 11 at 12:35
Peter Lawrey
438k55556952
Yeah, but I need to use Generics(? extends ObjectType) in collection
– Nagendhra Kumar Sunkara
Nov 11 at 12:40
@NagendhraKumarSunkara If you do, you won't be able to add anything to such a collection. Can you provide a more detailed example?
– Peter Lawrey
Nov 11 at 12:42
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
0
down vote
In general, I would use an interface rather than a class wherever possible as it is simpler and more flexible.
What you can write is
interface ObjectType { }
class Animal implements ObjectType { }
class Person implements ObjectType { }
List<ObjectType> objects = new ArrayList<>();
This might not do what you expect, however how you solve this depends on what you need the List to do.
answered Nov 11 at 12:35
Peter Lawrey
438k55556952
Yeah, but I need to use Generics(? extends ObjectType) in collection
– Nagendhra Kumar Sunkara
Nov 11 at 12:40
@NagendhraKumarSunkara If you do, you won't be able to add anything to such a collection. Can you provide a more detailed example?
– Peter Lawrey
Nov 11 at 12:42
add a comment |
up vote
0
down vote
In general, I would use an interface rather than a class wherever possible as it is simpler and more flexible.
What you can write is
interface ObjectType { }
class Animal implements ObjectType { }
class Person implements ObjectType { }
List<ObjectType> objects = new ArrayList<>();
This might not do what you expect, however how you solve this depends on what you need the List to do.
answered Nov 11 at 12:35
Peter Lawrey
438k55556952
Yeah, but I need to use Generics(? extends ObjectType) in collection
– Nagendhra Kumar Sunkara
Nov 11 at 12:40
@NagendhraKumarSunkara If you do, you won't be able to add anything to such a collection. Can you provide a more detailed example?
– Peter Lawrey
Nov 11 at 12:42
add a comment |
up vote
0
down vote
up vote
0
down vote
In general, I would use an interface rather than a class wherever possible as it is simpler and more flexible.
What you can write is
interface ObjectType { }
class Animal implements ObjectType { }
class Person implements ObjectType { }
List<ObjectType> objects = new ArrayList<>();
This might not do what you expect, however how you solve this depends on what you need the List to do.
answered Nov 11 at 12:35
Peter Lawrey
438k55556952
In general, I would use an interface rather than a class wherever possible as it is simpler and more flexible.
What you can write is
interface ObjectType { }
class Animal implements ObjectType { }
class Person implements ObjectType { }
List<ObjectType> objects = new ArrayList<>();
This might not do what you expect, however how you solve this depends on what you need the List to do.
answered Nov 11 at 12:35
Peter Lawrey
438k55556952
answered Nov 11 at 12:35
Peter Lawrey
438k55556952
answered Nov 11 at 12:35
Peter Lawrey
438k55556952
answered Nov 11 at 12:35
Peter Lawrey
438k55556952
438k55556952
Yeah, but I need to use Generics(? extends ObjectType) in collection
– Nagendhra Kumar Sunkara
Nov 11 at 12:40
@NagendhraKumarSunkara If you do, you won't be able to add anything to such a collection. Can you provide a more detailed example?
– Peter Lawrey
Nov 11 at 12:42
add a comment |
Yeah, but I need to use Generics(? extends ObjectType) in collection
– Nagendhra Kumar Sunkara
Nov 11 at 12:40
@NagendhraKumarSunkara If you do, you won't be able to add anything to such a collection. Can you provide a more detailed example?
– Peter Lawrey
Nov 11 at 12:42
Yeah, but I need to use Generics(? extends ObjectType) in collection
– Nagendhra Kumar Sunkara
Nov 11 at 12:40
Yeah, but I need to use Generics(? extends ObjectType) in collection
– Nagendhra Kumar Sunkara
Nov 11 at 12:40
@NagendhraKumarSunkara If you do, you won't be able to add anything to such a collection. Can you provide a more detailed example?
– Peter Lawrey
Nov 11 at 12:42
@NagendhraKumarSunkara If you do, you won't be able to add anything to such a collection. Can you provide a more detailed example?
– Peter Lawrey
Nov 11 at 12:42
add a comment |
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Can you mention your class implementation?
– GauravRai1512
Nov 11 at 12:33
public class ObjectType(){ public class Person extends ObjectType(){ public name,location,id,salary; //followed by a constructor for initialisation } then want to add perosn objects to arraylist as below List<? extends ObjectType> list=new ArrayList<Person>();
– Nagendhra Kumar Sunkara
Nov 11 at 12:35
If you are creating empty class then i would suggest to use interface rather then class and implement your animal and person class.
– GauravRai1512
Nov 11 at 12:37
There is one correction public class ObjectType{} rather then public class ObjectType(){}
– GauravRai1512
Nov 11 at 12:43
1
Don't put more information into comments, always update your question instead. Or can you really read that code only comments you made?
– GhostCat
Nov 11 at 12:45