Strange Java null behavior in Method Overloading [duplicate]

by

why the program calls foo(String x) instead of foo(Object x)

That is because String class extends from Object and hence is more specific to Object. So, compiler decides to invoke that method. Remember, Compiler always chooses the most specific method to invoke. See Section 15.12.5 of JLS

If more than one member method is both accessible and applicable to a
method invocation, it is necessary to choose one to provide the
descriptor for the run-time method dispatch. The Java programming
language uses the rule that the most specific method is chosen.

The informal intuition is that one method is more specific than
another if any invocation handled by the first method could be passed
on to the other one without a compile-time type error.

However, if you have two methods with parameter – String, and Integer, then you would get ambiguity error for null, as compiler cannot decide which one is more specific, as they are non-covariant types.

More Related Contents:

  1. Method Overloading for null argument
  2. Why does String.valueOf(null) throw a NullPointerException?
  3. How to do method overloading for null argument?
  4. Avoiding NullPointerException in Java
  5. Does Java support default parameter values?
  6. Properly removing an Integer from a List
  7. IllegalArgumentException or NullPointerException for a null parameter? [closed]
  8. Overload with different return type in Java?
  9. Constructor overloading in Java – best practice
  10. Java null check why use == instead of .equals()
  11. Check chains of “get” calls for null
  12. Null check chain vs catching NullPointerException
  13. How to check if my string is equal to null?
  14. Why can’t primitive data types be “null” in Java?
  15. Spark sql how to explode without losing null values
  16. Reference is ambiguous with generics
  17. bug with varargs and overloading?
  18. Is null check needed before calling instanceof?
  19. Lambda expression and method overloading doubts
  20. Java erasure with generic overloading (not overriding)
  21. Why use Optional.of over Optional.ofNullable?
  22. Should Optional.ofNullable() be used for null check?
  23. Is null an Object?
  24. Hibernate order by with nulls last
  25. Understanding the difference between null and ‘\u000’ in Java
  26. Java, What is the difference between assigning null to object and just declaration
  27. Java: Exception itself is null
  28. Overriding a method with different return types in java?
  29. Compilers behave differently with a null parameter of a generic method
  30. How do overloaded methods work?

Leave a Comment