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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.lang.reflect.*;
  6. import java.io.*;
  7.  
  8. /* Name of the class has to be "Main" only if the class is public. */
  9. class Ideone
  10. {
  11. enum EagerInitializedSingleton { INSTANCE }
  12.  
  13. public static void main (String[] args) throws java.lang.Exception
  14. {
  15. Constructor[] constructors = EagerInitializedSingleton.class.getDeclaredConstructors();
  16. for (Constructor constructor : constructors) {
  17. //Below code will destroy the singleton pattern
  18. constructor.setAccessible(true);
  19. System.out.println((EagerInitializedSingleton) constructor.newInstance());
  20. }
  21. }
  22. }
Runtime error #stdin #stdout #stderr 0.09s 320576KB
stdin
Standard input is empty
stdout
Standard output is empty
stderr
Exception in thread "main" java.lang.IllegalArgumentException: Cannot reflectively create enum objects
	at java.lang.reflect.Constructor.newInstance(Constructor.java:416)
	at Ideone.main(Main.java:19)