instanceof error

[qhyang]

Hi there,
I have two classes named Address and Person. I also make one instance for Address and one instance for Person. Then I have the following code:
Person p = new Person();
Address a = new Address();
if(p instanceof Person)
......
if(a instanceof Address)
....
if(a instance of Person) //check
.....
When I compile, it gave me error "inconvertible types
found : com.berkley.training.util.Person
required: com.berkley.training.util.Address
if(p instanceof Address)"
I am not sure why it is a compile error instead of run-time error.
Thanks!
qionghua
^

[Anonymous]

testing your code like this:

public MainTest()
  {
    [B]Object[/B] p = new Person();
    [B]Object[/B] a = new Address();
    if(p instanceof Person)
    {
      System.out.println("p instanceof Person");
    }
    else
    {
      System.out.println("p not instanceof Person");
    }
    if(a instanceof Address)
    {
      System.out.println("a instanceof Address");
    }
    else
    {
      System.out.println("a not instanceof Adress");
    }
     if(a instanceof Person)
    {
      System.out.println("a instanceof Person");
    }
    else
    {
      System.out.println("a not instanceof Person");
    }
    if(p instanceof Address)
    {
      System.out.println("p instanceof Address");
    }
    else
    {
      System.out.println("p not instanceof Adress");
    }
  }

You have no more the compiler error. I think that the compiler check for easy instanceof test before compiling. But i don't know much about the compiler behaviour!
if someone know better ! let explain
------------------
Benjamin l�onard
www.evisor.com
[This message has been edited by Benjamin Leonard (edited May 22, 2001).]

[Art Metzer]

From the Java Language Specification,

If a cast of the RelationalExpression to the ReferenceType would be rejected as a compile-time error, then the instanceof relational expression likewise produces a compile-time error.

Art

[Cindy Glass]

qhyang,
Please change your name to be compliant with JavaRanch's naming policy.
Your ID should be 2 separate names with more than 1 letter each. We really want this to be a professional forum and would prefer that you use your REAL name.
Thanks,
Cindy

[qionghua yang]

sorry, I used my old Id again.