Passing value from one method to the next

[James Farber]

Just as the subject implies, I'm having difficulty trying to pass a value from one method to the next in the same class. I know it has to do with object creation, but I can't quite get it working. Some sample code of what I'm trying to do:

     public class Example{
 

   public void justSomeMethod(){
 
   short number=1;

   //code

           number++;
 
   }
 
 public void differentMethod(){
 
 //how do i pass the incremented value of number into  this method?

         System.out.println("incremented number variable here");
 
 }
 

public static void main (String[] args){

Example d=new Example();

             d.differentMethod();


}

}

[David McCombs]

Make number a class level variable. In your code you never call justSomeMethod, so number never gets initialized or incremented.

 
public class Example{
 private short number;
 
//number will get set to 0 when the default constructor is called
 
public void justSomeMethod(){
       number++;
 
}
 
public void differentMethod(){
 


         System.out.println(number);
 
 }
 

[fred rosenberger]

You have declared number inside the justSomeMethod(). That makes it a local variable. In other words, that variable only exists inside that method.

in your main, you create an Example d. You call d.differentMethod(). At this point, since you've never entered the justSomeMethod method, the variable you are trying to acces does not exist.

David shows you how to move your local variable to become a member variable. Now it will exist as soon as an instance of the class is created. When you then call your differentMethod, you can access the variable.

[James Farber]

Thanks for the help guys!

[Garrett Rowe]

Wow, I would have gone in a totally different direction and assume that if differentMethod() needed a number, it should be passed one as a parameter, especially if no other behavior of Example class depends on the current state of the *number* variable.

[James Farber]

That's what I was doing initially, trying to pass it as a parameter. I couldn't quite get that down. I know a bit of C++ and can pass values between functions that way (or at least I used to know how a few years back), but I just couldn't figure it out in Java. Honestly, parameter passing would be ideal for me in this situation, since I'm now having issues of passing all sorts of different values, including values to/from methods in separate classes.

[David McCombs]

See if you can follow this.

public class Example
{
   public static void main(String[] args)
   {
      int val=5;
      val=someMethod(val);
      System.out.println(val);
      val=anotherMethod(val);
      System.out.println(val);
 
      val=0;
      thisMethod(val);
      System.out.println(val);//what do you think val should be here?
   }
 
   public static void thisMethod(int val)
   {
      val=1000;
   }
   public static int someMethod(int val)
   {
      val++;
      return val;
   }
 
   public static int anotherMethod(int val)
   {
      int num=10;
      num+=val;
      return num;
   }
}
 

[ February 03, 2007: Message edited by: David McCombs ]

[James Farber]

I can follow it. Tricked me at first, but I got it now. How does an object get passed between parameters? Passing the object from one parameter to the next in the same class is the same as passing it between parameters in different classes, right? Sorry if I'm asking too many questions for this thread.