Java 9 replace Class.newInstance












13














Class.newInstance was deprecated in Java 9:




clazz.newInstance()


can be replaced by



clazz.getDeclaredConstructor().newInstance()



The problem is that getDeclaredConstructor returns any constructor without regarding the access level.



If I want to replace all occurrences in my code (on different packages/access level) should I use getConstructor to get the public constructor?




the Constructor object of the public constructor that matches the specified parameterTypes




Or can't I bulk replace all occurrences because it needs to be per case (if a public constructor exists and/or if I have the right access level for the class)?



EDIT



getDeclaredConstructor:




   return getConstructor0(parameterTypes, Member.DECLARED);



getConstructor:




   return getConstructor0(parameterTypes, Member.PUBLIC);






java reflection constructor java-9







share|improve this question




















  • 1




    If you need to access constructor at different levels, getDeclaredConstructor(s) is the only way out. Can't you use getDeclaredConstructors​() (not getDeclaredConstructor()) to get all constructors and replace one depending on your logic?
    – Sukhpal Singh
    Nov 12 at 7:02






  • 5




    As the deprecation message says, the equivalent code to clazz.newInstance() is clazz.getDeclaredConstructor().newInstance(). I would assume this means that anywhere you're successfully using clazz.newInstance() can be replaced with the recommended code. If you replace clazz.newInstance() with clazz.getConstructor().newInstance() you're changing the semantics of the code.
    – Slaw
    Nov 12 at 7:04








  • 2




    I haven’t tried, but I wouldn’t expect clazz.newInstance() to work either if the zero-arg constructor isn’t public — does it?? So what would you be losing in practice by using clazz.getDeclaredConstructor().newInstance() instead?
    – Ole V.V.
    Nov 12 at 7:22






  • 2




    @OleV.V. Yes, Class.newInstance() works with non-public constructors. But it requires you to have the proper access else it throws an IllegalAccessException (from some quick, non-exhaustive testing).
    – Slaw
    Nov 12 at 7:28








  • 5




    Related (on the reasons why it was deprecated): stackoverflow.com/questions/195321/…
    – Hulk
    Nov 12 at 8:09
















13














Class.newInstance was deprecated in Java 9:




clazz.newInstance()


can be replaced by



clazz.getDeclaredConstructor().newInstance()



The problem is that getDeclaredConstructor returns any constructor without regarding the access level.



If I want to replace all occurrences in my code (on different packages/access level) should I use getConstructor to get the public constructor?




the Constructor object of the public constructor that matches the specified parameterTypes




Or can't I bulk replace all occurrences because it needs to be per case (if a public constructor exists and/or if I have the right access level for the class)?



EDIT



getDeclaredConstructor:




   return getConstructor0(parameterTypes, Member.DECLARED);



getConstructor:




   return getConstructor0(parameterTypes, Member.PUBLIC);






java reflection constructor java-9







share|improve this question




















  • 1




    If you need to access constructor at different levels, getDeclaredConstructor(s) is the only way out. Can't you use getDeclaredConstructors​() (not getDeclaredConstructor()) to get all constructors and replace one depending on your logic?
    – Sukhpal Singh
    Nov 12 at 7:02






  • 5




    As the deprecation message says, the equivalent code to clazz.newInstance() is clazz.getDeclaredConstructor().newInstance(). I would assume this means that anywhere you're successfully using clazz.newInstance() can be replaced with the recommended code. If you replace clazz.newInstance() with clazz.getConstructor().newInstance() you're changing the semantics of the code.
    – Slaw
    Nov 12 at 7:04








  • 2




    I haven’t tried, but I wouldn’t expect clazz.newInstance() to work either if the zero-arg constructor isn’t public — does it?? So what would you be losing in practice by using clazz.getDeclaredConstructor().newInstance() instead?
    – Ole V.V.
    Nov 12 at 7:22






  • 2




    @OleV.V. Yes, Class.newInstance() works with non-public constructors. But it requires you to have the proper access else it throws an IllegalAccessException (from some quick, non-exhaustive testing).
    – Slaw
    Nov 12 at 7:28








  • 5




    Related (on the reasons why it was deprecated): stackoverflow.com/questions/195321/…
    – Hulk
    Nov 12 at 8:09














13












13








13


4





Class.newInstance was deprecated in Java 9:




clazz.newInstance()


can be replaced by



clazz.getDeclaredConstructor().newInstance()



The problem is that getDeclaredConstructor returns any constructor without regarding the access level.



If I want to replace all occurrences in my code (on different packages/access level) should I use getConstructor to get the public constructor?




the Constructor object of the public constructor that matches the specified parameterTypes




Or can't I bulk replace all occurrences because it needs to be per case (if a public constructor exists and/or if I have the right access level for the class)?



EDIT



getDeclaredConstructor:




   return getConstructor0(parameterTypes, Member.DECLARED);



getConstructor:




   return getConstructor0(parameterTypes, Member.PUBLIC);






java reflection constructor java-9







share|improve this question















Class.newInstance was deprecated in Java 9:




clazz.newInstance()


can be replaced by



clazz.getDeclaredConstructor().newInstance()



The problem is that getDeclaredConstructor returns any constructor without regarding the access level.



If I want to replace all occurrences in my code (on different packages/access level) should I use getConstructor to get the public constructor?




the Constructor object of the public constructor that matches the specified parameterTypes




Or can't I bulk replace all occurrences because it needs to be per case (if a public constructor exists and/or if I have the right access level for the class)?



EDIT



getDeclaredConstructor:




   return getConstructor0(parameterTypes, Member.DECLARED);



getConstructor:




   return getConstructor0(parameterTypes, Member.PUBLIC);






java reflection constructor java-9




java reflection constructor java-9






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 13 at 14:33









Holger

162k23229435




162k23229435










asked Nov 12 at 6:44









user7294900

20.4k103258




20.4k103258








  • 1




    If you need to access constructor at different levels, getDeclaredConstructor(s) is the only way out. Can't you use getDeclaredConstructors​() (not getDeclaredConstructor()) to get all constructors and replace one depending on your logic?
    – Sukhpal Singh
    Nov 12 at 7:02






  • 5




    As the deprecation message says, the equivalent code to clazz.newInstance() is clazz.getDeclaredConstructor().newInstance(). I would assume this means that anywhere you're successfully using clazz.newInstance() can be replaced with the recommended code. If you replace clazz.newInstance() with clazz.getConstructor().newInstance() you're changing the semantics of the code.
    – Slaw
    Nov 12 at 7:04








  • 2




    I haven’t tried, but I wouldn’t expect clazz.newInstance() to work either if the zero-arg constructor isn’t public — does it?? So what would you be losing in practice by using clazz.getDeclaredConstructor().newInstance() instead?
    – Ole V.V.
    Nov 12 at 7:22






  • 2




    @OleV.V. Yes, Class.newInstance() works with non-public constructors. But it requires you to have the proper access else it throws an IllegalAccessException (from some quick, non-exhaustive testing).
    – Slaw
    Nov 12 at 7:28








  • 5




    Related (on the reasons why it was deprecated): stackoverflow.com/questions/195321/…
    – Hulk
    Nov 12 at 8:09














  • 1




    If you need to access constructor at different levels, getDeclaredConstructor(s) is the only way out. Can't you use getDeclaredConstructors​() (not getDeclaredConstructor()) to get all constructors and replace one depending on your logic?
    – Sukhpal Singh
    Nov 12 at 7:02






  • 5




    As the deprecation message says, the equivalent code to clazz.newInstance() is clazz.getDeclaredConstructor().newInstance(). I would assume this means that anywhere you're successfully using clazz.newInstance() can be replaced with the recommended code. If you replace clazz.newInstance() with clazz.getConstructor().newInstance() you're changing the semantics of the code.
    – Slaw
    Nov 12 at 7:04








  • 2




    I haven’t tried, but I wouldn’t expect clazz.newInstance() to work either if the zero-arg constructor isn’t public — does it?? So what would you be losing in practice by using clazz.getDeclaredConstructor().newInstance() instead?
    – Ole V.V.
    Nov 12 at 7:22






  • 2




    @OleV.V. Yes, Class.newInstance() works with non-public constructors. But it requires you to have the proper access else it throws an IllegalAccessException (from some quick, non-exhaustive testing).
    – Slaw
    Nov 12 at 7:28








  • 5




    Related (on the reasons why it was deprecated): stackoverflow.com/questions/195321/…
    – Hulk
    Nov 12 at 8:09








1




1




If you need to access constructor at different levels, getDeclaredConstructor(s) is the only way out. Can't you use getDeclaredConstructors​() (not getDeclaredConstructor()) to get all constructors and replace one depending on your logic?
– Sukhpal Singh
Nov 12 at 7:02




If you need to access constructor at different levels, getDeclaredConstructor(s) is the only way out. Can't you use getDeclaredConstructors​() (not getDeclaredConstructor()) to get all constructors and replace one depending on your logic?
– Sukhpal Singh
Nov 12 at 7:02




5




5




As the deprecation message says, the equivalent code to clazz.newInstance() is clazz.getDeclaredConstructor().newInstance(). I would assume this means that anywhere you're successfully using clazz.newInstance() can be replaced with the recommended code. If you replace clazz.newInstance() with clazz.getConstructor().newInstance() you're changing the semantics of the code.
– Slaw
Nov 12 at 7:04






As the deprecation message says, the equivalent code to clazz.newInstance() is clazz.getDeclaredConstructor().newInstance(). I would assume this means that anywhere you're successfully using clazz.newInstance() can be replaced with the recommended code. If you replace clazz.newInstance() with clazz.getConstructor().newInstance() you're changing the semantics of the code.
– Slaw
Nov 12 at 7:04






2




2




I haven’t tried, but I wouldn’t expect clazz.newInstance() to work either if the zero-arg constructor isn’t public — does it?? So what would you be losing in practice by using clazz.getDeclaredConstructor().newInstance() instead?
– Ole V.V.
Nov 12 at 7:22




I haven’t tried, but I wouldn’t expect clazz.newInstance() to work either if the zero-arg constructor isn’t public — does it?? So what would you be losing in practice by using clazz.getDeclaredConstructor().newInstance() instead?
– Ole V.V.
Nov 12 at 7:22




2




2




@OleV.V. Yes, Class.newInstance() works with non-public constructors. But it requires you to have the proper access else it throws an IllegalAccessException (from some quick, non-exhaustive testing).
– Slaw
Nov 12 at 7:28






@OleV.V. Yes, Class.newInstance() works with non-public constructors. But it requires you to have the proper access else it throws an IllegalAccessException (from some quick, non-exhaustive testing).
– Slaw
Nov 12 at 7:28






5




5




Related (on the reasons why it was deprecated): stackoverflow.com/questions/195321/…
– Hulk
Nov 12 at 8:09




Related (on the reasons why it was deprecated): stackoverflow.com/questions/195321/…
– Hulk
Nov 12 at 8:09












1 Answer
1






active

oldest

votes


















8














Class.newInstance() invokes the zero-argument constructor, whether it is public or not. It performs a runtime check of the caller's access to that constructor.



Calling getDeclaredConstructor() returns that same constructor. Calling getDeclaredConstructor().newInstance() performs the same runtime checks. Except for the different handling of exceptions, it does the same thing.



No, don't change it to getConstructor(). That would cause a NoSuchMethodException for non-public constructors.






share|improve this answer





















  • Thank you, so any exceptions thrown will only be a valid initialization failures?
    – user7294900
    Nov 12 at 17:03












  • @user7294900 Yes.
    – Boann
    Nov 12 at 22:22











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1 Answer
1






active

oldest

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1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









8














Class.newInstance() invokes the zero-argument constructor, whether it is public or not. It performs a runtime check of the caller's access to that constructor.



Calling getDeclaredConstructor() returns that same constructor. Calling getDeclaredConstructor().newInstance() performs the same runtime checks. Except for the different handling of exceptions, it does the same thing.



No, don't change it to getConstructor(). That would cause a NoSuchMethodException for non-public constructors.






share|improve this answer





















  • Thank you, so any exceptions thrown will only be a valid initialization failures?
    – user7294900
    Nov 12 at 17:03












  • @user7294900 Yes.
    – Boann
    Nov 12 at 22:22
















8














Class.newInstance() invokes the zero-argument constructor, whether it is public or not. It performs a runtime check of the caller's access to that constructor.



Calling getDeclaredConstructor() returns that same constructor. Calling getDeclaredConstructor().newInstance() performs the same runtime checks. Except for the different handling of exceptions, it does the same thing.



No, don't change it to getConstructor(). That would cause a NoSuchMethodException for non-public constructors.






share|improve this answer





















  • Thank you, so any exceptions thrown will only be a valid initialization failures?
    – user7294900
    Nov 12 at 17:03












  • @user7294900 Yes.
    – Boann
    Nov 12 at 22:22














8












8








8






Class.newInstance() invokes the zero-argument constructor, whether it is public or not. It performs a runtime check of the caller's access to that constructor.



Calling getDeclaredConstructor() returns that same constructor. Calling getDeclaredConstructor().newInstance() performs the same runtime checks. Except for the different handling of exceptions, it does the same thing.



No, don't change it to getConstructor(). That would cause a NoSuchMethodException for non-public constructors.






share|improve this answer












Class.newInstance() invokes the zero-argument constructor, whether it is public or not. It performs a runtime check of the caller's access to that constructor.



Calling getDeclaredConstructor() returns that same constructor. Calling getDeclaredConstructor().newInstance() performs the same runtime checks. Except for the different handling of exceptions, it does the same thing.



No, don't change it to getConstructor(). That would cause a NoSuchMethodException for non-public constructors.







share|improve this answer












share|improve this answer



share|improve this answer










answered Nov 12 at 15:22









Boann

36.7k1287121




36.7k1287121












  • Thank you, so any exceptions thrown will only be a valid initialization failures?
    – user7294900
    Nov 12 at 17:03












  • @user7294900 Yes.
    – Boann
    Nov 12 at 22:22


















  • Thank you, so any exceptions thrown will only be a valid initialization failures?
    – user7294900
    Nov 12 at 17:03












  • @user7294900 Yes.
    – Boann
    Nov 12 at 22:22
















Thank you, so any exceptions thrown will only be a valid initialization failures?
– user7294900
Nov 12 at 17:03






Thank you, so any exceptions thrown will only be a valid initialization failures?
– user7294900
Nov 12 at 17:03














@user7294900 Yes.
– Boann
Nov 12 at 22:22




@user7294900 Yes.
– Boann
Nov 12 at 22:22


















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