Passing an arguament to a method and defining type

[Matt Player]

Hi there, probably easier to give code than to explain so:

  class Dog {
   int size;
   String bark;
   int nob;

   void bark(nob) {
      if (size > 60) {
         while (nob > 0) {
            System.out.println("Woof!");
            nob = nob - 1;
         }
      }
      else if (size > 14) {
         while (nob > 0) {
            System.out.println("Woof!");
            nob = nob - 1;
         }
      }
      else {
         while (nob > 0) {
            System.out.println("Woof!");
            nob = nob - 1;
         }
      } 
   }
}

class DogTestDrive {
   public static void main (String[] args) {
      Dog[] aDog = new Dog[3];
      int x=0;
      while (x<3) {
         aDog[x] = new Dog();
         x = x + 1;
      }
      aDog[0].size = 70;
      aDog[1].size = 8;
      aDog[2].size = 35;
      aDog[0].nob = 3;
      aDog[1].nob = 4;
      aDog[2].nob = 5;

      aDog[0].bark(3);
      aDog[1].bark(3);
      aDog[2].bark(3);
   }
}  

and when I try to compile this I get the error:

DogTestDrive.java:6: <identifier> expected
void bark(nob) {
^
DogTestDrive.java:26: ')' expected
}
^
2 errors
Powerbook:~/javaeg matt$ javac DogTestDrive.java
DogTestDrive.java:6: <identifier> expected
void bark(nob) {
^
DogTestDrive.java:26: ')' expected
}
^
2 errors

Now it seems to be telling me that I need to identify my variable "nob" (or number of barks... of course!) but I have already declared as a variable at the top.

Please tell me why this no work??

Cheers

Matt

[fred rosenberger]

you have declared nob as an instance variable for the class. That means that each and every 'Dog' object will have an integer called 'nob'.

Then you declare (create) a method. You have to explicitly list out what kind of variables you are passing into each method. So, assuming you want this to be an 'int' , you need to declare your method as

void bark (int nob)

Note then that the 'nob' variable used inside the method is DIFFERENT than the 'nob' defined for the class. They are distinct and separate.

[Matt Player]

you have declared nob as an instance variable for the class. That means that each and every 'Dog' object will have an integer called 'nob'.

Can I not reference this within the method then?

[Balu Sadhasivam]

You can very well use it using "this" keyword (this.nob). "this" refers to the current instance which invoked the instance method (void bark).

Fred meant that since you have passed nob as parameter , it acts as a local variable and is distinct and separate from the instance variable "nob'

[fred rosenberger]

you can, but you have to let java know which one you mean. And that requires you to know which one you mean.

if you want to use the member variable, then why are you passing it into the method? In other words, if you changed your method to this:

void bark(numberOfBarks) {  
//code here
}

inside the method, you could refer to numberOfBarks (which is local to the method), or you could refer to nob, which is part of the class.

My guess is that you want to use numberOfBarks, because otherwise you'll permanently change the nob value inside your method.