Overloading question

[Jeeny Dorph]

 
class test {
  void method(Object o) { System.out.println("object"); }
  void method(Object[] o) { System.out.println("array"); }
  public static void main(String[] args) {
    new test().method(null);
  }
}

This code compiles fine and prints out "array". Is the method declaration "void method(Object[] o)" more specific than "void method(Object o)"?

[Rishi Wright]

Hi Jeeny,
whenever a overloaded method was called with a parameter that can be assaignable to more than one overloaded method ,
then the method whose parameter(s) are assaignable to other method parameter type will be called.
In your example u can always assaign Object[]o type to the reference of type Object(i.e Object o in your case)
Hope u got it.
rishi

[Cathy Song]

Hi All
I still do not understand why "array" is printed out..
Could some help please?
Thanks,
Cathy.

[Jeeny Dorph]

Thanx, Rishi!
I got it

[Anupam Sinha]

Hi Cathy
The point is that Object's array is assignable to Object because an array is also an Object. But the reverse is not true. That is there is no gaurantee that an array will always be an Object. Hence array is printed.

[Raja Sagar Panamgipalli]

Hey Anupam did u mean an array can be of primitive type true ..the reverse cannot be true..
thanx.

[Steve Lovelace]

Did some experimenting and it seems like the compiler is working very hard to find the most specific method that could possible work. I amplified the example a bit.

public class Test {
public static void main(String[] args) {
new A().method(null); // 1
new A().method(new String[] {"1"});
}
void method(Object o) { System.out.println("object"); }
void method(Object[] o) { System.out.println("object array"); }
void method(Integer[] o) { System.out.println("integer array"); }
void method(Float[] o) { System.out.println("float array"); } // 2
} 

As is the compiler complains about not being able to decide between Integer[] and Float[]. But if line 1 is commented out, "object array" prints. If line 1 is uncommented and line 2 is commented, "integer array" and "object array" prints.