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Difference between List super T> and List

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-1

I was going through generics in Java and I'm having trouble trying to understand where I would use the following two.

I understand that the first myList would ensure that the list only contains elements of type Integer and all it's superclasses. Now I'm trying to figure out where myList2 would fit in here.

List<? super Integer> myList;
List<Class<? super Integer>> myList2;

Edit: It's not a duplicate of the question being linked...since this is clearly regarding the use of ? vs Class<? whereas the other question is about super vs extend

java

share|improve this question

edited Mar 25 at 21:37

AsadSMalik

asked Mar 25 at 21:26

AsadSMalikAsadSMalik

34799 silver badges2727 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  myList2.add(Integer.class);
  
  – Ruslan
  Mar 25 at 21:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Possible duplicate of What is a difference between <? super E> and <? extends E>?
  
  – LppEdd
  Mar 25 at 21:32
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  myList is a list of object instances, e.g. a List<Number> storing Integer, Double, BigDecimal, ... objects, such as 42, 3.14159, 3e9876, ... --- myList2 is a list of Class objects, i.e. a list of Integer.class, Number.class, Object.class, Serializable.class, or Comparable.class values.
  
  – Andreas
  Mar 25 at 21:33
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I understand the difference between super and extends. I was just wondering where myList2 would be used.
  
  – AsadSMalik
  Mar 25 at 21:33
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  I can't offhand think of a use for a list of class objects, but in general you use a Class object as a way to indicate type, or as a way to determine the properties of that type.
  
  – another-dave
  Mar 25 at 21:53
  

  
  
  
  

 | 
show 1 more comment

-1

I was going through generics in Java and I'm having trouble trying to understand where I would use the following two.

I understand that the first myList would ensure that the list only contains elements of type Integer and all it's superclasses. Now I'm trying to figure out where myList2 would fit in here.

List<? super Integer> myList;
List<Class<? super Integer>> myList2;

Edit: It's not a duplicate of the question being linked...since this is clearly regarding the use of ? vs Class<? whereas the other question is about super vs extend

java

share|improve this question

edited Mar 25 at 21:37

AsadSMalik

asked Mar 25 at 21:26

AsadSMalikAsadSMalik

34799 silver badges2727 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  myList2.add(Integer.class);
  
  – Ruslan
  Mar 25 at 21:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Possible duplicate of What is a difference between <? super E> and <? extends E>?
  
  – LppEdd
  Mar 25 at 21:32
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  myList is a list of object instances, e.g. a List<Number> storing Integer, Double, BigDecimal, ... objects, such as 42, 3.14159, 3e9876, ... --- myList2 is a list of Class objects, i.e. a list of Integer.class, Number.class, Object.class, Serializable.class, or Comparable.class values.
  
  – Andreas
  Mar 25 at 21:33
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I understand the difference between super and extends. I was just wondering where myList2 would be used.
  
  – AsadSMalik
  Mar 25 at 21:33
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  I can't offhand think of a use for a list of class objects, but in general you use a Class object as a way to indicate type, or as a way to determine the properties of that type.
  
  – another-dave
  Mar 25 at 21:53
  

  
  
  
  

 | 
show 1 more comment

I was going through generics in Java and I'm having trouble trying to understand where I would use the following two.

I understand that the first myList would ensure that the list only contains elements of type Integer and all it's superclasses. Now I'm trying to figure out where myList2 would fit in here.

List<? super Integer> myList;
List<Class<? super Integer>> myList2;

Edit: It's not a duplicate of the question being linked...since this is clearly regarding the use of ? vs Class<? whereas the other question is about super vs extend

java

share|improve this question

edited Mar 25 at 21:37

AsadSMalik

asked Mar 25 at 21:26

AsadSMalikAsadSMalik

34799 silver badges2727 bronze badges

List<? super Integer> myList;
List<Class<? super Integer>> myList2;

share|improve this question

edited Mar 25 at 21:37

AsadSMalik

asked Mar 25 at 21:26

AsadSMalikAsadSMalik

34799 silver badges2727 bronze badges

share|improve this question

edited Mar 25 at 21:37

AsadSMalik

asked Mar 25 at 21:26

AsadSMalikAsadSMalik

34799 silver badges2727 bronze badges

asked Mar 25 at 21:26

AsadSMalikAsadSMalik

34799 silver badges2727 bronze badges

asked Mar 25 at 21:26

AsadSMalikAsadSMalik

34799 silver badges2727 bronze badges

2 Answers
2

active

oldest

votes

1

The first one, 'myList' may contain integer values. Example: myList.add(200);

The second one, 'myList2' may contain classes of type integer. Example: myList2.add(Integer.class);

share|improve this answer

answered Mar 25 at 21:33

Andreas VoglAndreas Vogl

77355 silver badges1212 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Ok so like you mentioned in the comments, if instead of Integer, I'm extending Number, then the second list could contain elements Integer, BigDecimal etc.
  
  – AsadSMalik
  Mar 25 at 21:34
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The first list might also contain e.g. String values, because it might be a List<Object>. --- The second list can also store classes of other types, e.g. Number.class, Object.class, Serializable.class, and Comparable.class.
  
  – Andreas
  Mar 25 at 21:35
  
  

  
  
  
  

add a comment | 

0

The first list contains objects of Integer and its superclasses.

The second one contains class objects (or simply classes) of Integer and its superclasses, i.e:

Integer.class;
Number.class;

You can read more about the differences here: The difference between Classes, Objects, and Instances

share|improve this answer

edited Mar 25 at 21:56

answered Mar 25 at 21:33

Pavel SmirnovPavel Smirnov

2,76922 gold badges99 silver badges1818 bronze badges

add a comment | 

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1

The first one, 'myList' may contain integer values. Example: myList.add(200);

The second one, 'myList2' may contain classes of type integer. Example: myList2.add(Integer.class);

share|improve this answer

answered Mar 25 at 21:33

Andreas VoglAndreas Vogl

77355 silver badges1212 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Ok so like you mentioned in the comments, if instead of Integer, I'm extending Number, then the second list could contain elements Integer, BigDecimal etc.
  
  – AsadSMalik
  Mar 25 at 21:34
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The first list might also contain e.g. String values, because it might be a List<Object>. --- The second list can also store classes of other types, e.g. Number.class, Object.class, Serializable.class, and Comparable.class.
  
  – Andreas
  Mar 25 at 21:35
  
  

  
  
  
  

add a comment | 

1

The first one, 'myList' may contain integer values. Example: myList.add(200);

The second one, 'myList2' may contain classes of type integer. Example: myList2.add(Integer.class);

share|improve this answer

answered Mar 25 at 21:33

Andreas VoglAndreas Vogl

77355 silver badges1212 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Ok so like you mentioned in the comments, if instead of Integer, I'm extending Number, then the second list could contain elements Integer, BigDecimal etc.
  
  – AsadSMalik
  Mar 25 at 21:34
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The first list might also contain e.g. String values, because it might be a List<Object>. --- The second list can also store classes of other types, e.g. Number.class, Object.class, Serializable.class, and Comparable.class.
  
  – Andreas
  Mar 25 at 21:35
  
  

  
  
  
  

add a comment | 

The first one, 'myList' may contain integer values. Example: myList.add(200);

The second one, 'myList2' may contain classes of type integer. Example: myList2.add(Integer.class);

share|improve this answer

answered Mar 25 at 21:33

Andreas VoglAndreas Vogl

77355 silver badges1212 bronze badges

share|improve this answer

answered Mar 25 at 21:33

Andreas VoglAndreas Vogl

77355 silver badges1212 bronze badges

answered Mar 25 at 21:33

Andreas VoglAndreas Vogl

77355 silver badges1212 bronze badges

answered Mar 25 at 21:33

Andreas VoglAndreas Vogl

77355 silver badges1212 bronze badges

0

The first list contains objects of Integer and its superclasses.

The second one contains class objects (or simply classes) of Integer and its superclasses, i.e:

Integer.class;
Number.class;

You can read more about the differences here: The difference between Classes, Objects, and Instances

share|improve this answer

edited Mar 25 at 21:56

answered Mar 25 at 21:33

Pavel SmirnovPavel Smirnov

2,76922 gold badges99 silver badges1818 bronze badges

add a comment | 

0

The first list contains objects of Integer and its superclasses.

The second one contains class objects (or simply classes) of Integer and its superclasses, i.e:

Integer.class;
Number.class;

You can read more about the differences here: The difference between Classes, Objects, and Instances

share|improve this answer

edited Mar 25 at 21:56

answered Mar 25 at 21:33

Pavel SmirnovPavel Smirnov

2,76922 gold badges99 silver badges1818 bronze badges

add a comment | 

The first list contains objects of Integer and its superclasses.

The second one contains class objects (or simply classes) of Integer and its superclasses, i.e:

Integer.class;
Number.class;

You can read more about the differences here: The difference between Classes, Objects, and Instances

share|improve this answer

edited Mar 25 at 21:56

answered Mar 25 at 21:33

Pavel SmirnovPavel Smirnov

2,76922 gold badges99 silver badges1818 bronze badges

Integer.class;
Number.class;

share|improve this answer

edited Mar 25 at 21:56

answered Mar 25 at 21:33

Pavel SmirnovPavel Smirnov

2,76922 gold badges99 silver badges1818 bronze badges

answered Mar 25 at 21:33

Pavel SmirnovPavel Smirnov

2,76922 gold badges99 silver badges1818 bronze badges

answered Mar 25 at 21:33

Pavel SmirnovPavel Smirnov

2,76922 gold badges99 silver badges1818 bronze badges