Variable scope and assignment

[michael bradly]

I've been working on a problem dealing with recursion, and I need to count the number of calls to the recursive method.
I'm stumped.
If I have a variable assigned in the method, everytime it enters the method it will get reassigned so I lose my track count.
Since I am returning an integer from the method already, I can't return a count.
The only thing I can think of is passing another arguement in my method header that has a static variable count to keep track of the number of calls to the method.
Does this sound about right?
Regards, Michael

[Anthony Villanueva]

I suppose you can use an instance variable as a counter. Using a static variable may be dangerous, if you use many instances of this class:

public class Test55
{
int counter;
public static void main (String[] args)
{
new Test55().doItAgain(5);
}
void doItAgain(int i)
{
if (i == 0) return;
System.out.println("Doing it... " + ++counter);
doItAgain(i-1);
}
}

[Ron Newman]

You could pass an int[] array, of length 1, as an additional argument to the method. The method should increment the 0'th element of the array before doing anything else.
That avoids the need for a static variable, which is generally best to avoid if you ever want to do multi-threading.

[michael bradly]

This is similar to what I was trying. However, where does the counter get initialized with a value?
If I try it like you have it, I get:
C:\JavaEx\entryTest\entryTest.java:27: unreachable statement
System.out.println("The number of rec calls is" + ++recCount);
Thx for the quick responses, Michael

Originally posted by Anthony Villanueva:
I suppose you can use an instance variable as a counter. Using a static variable may be dangerous, if you use many instances of this class:

public class Test55
{
int counter;
public static void main (String[] args)
{
new Test55().doItAgain(5);
}
void doItAgain(int i)
{
if (i == 0) return;
System.out.println("Doing it... " + ++counter);
doItAgain(i-1);
}
}

[Anthony Villanueva]

Originally posted by michael bradly:
This is similar to what I was trying. However, where does the counter get initialized with a value?

If a non-final instance variable is not explicitly initialized it will have a default value. In the case of int, the default value is 0.
Can you post your code?

[michael bradly]

Sure can... here is the code I am working on...

public class entryTest
{
   public static int maxArray(int[] anArray, int first, int last) 
   {
      System.out.println("Entry into the method: ");
      int midpoint;
      int maxNum;
      int maxNum2;
      int recCount;
      //System.out.println("Testing value of variables, midpoint:" + midpoint + "maxNum: " + maxNum
      //+ "maxNum2: " + maxNum2);
      
      //BASE CASE***************************************************************************
      if (last == first)
      {  
         return anArray[0];
         System.out.println("The number of rec calls is" + ++recCount);
      }      
         
      else
      {   
         //create the midpoint
         midpoint = (first + last)/2;
         //System.out.println("Testing midpoint in base case: " + midpoint);
     
         //find the largest value in the left half of the array
         maxNum = maxArray(anArray, first, midpoint);
        //System.out.println("Testing maxNum in recursion call" + maxNum);
         
         if (anArray[midpoint] > maxNum)
         {
            maxNum = anArray[midpoint];
            System.out.println ("Testing maxNum comparision to anArray[midpoint]" + maxNum);
            
            //return maxNum;
         }
         
         // find the largest value in the right half of the array
         maxNum2 = maxArray(anArray, midpoint+1, last);
                 
         //System.out.println("Testing maxNum2 in recursion call" + maxNum2);
         
         if (anArray[midpoint+1] > maxNum2)
         {
            maxNum2 = anArray[midpoint+1];
            System.out.println ("Testing maxNum comparision to anArray[midpoint]" + maxNum2);
            
            //return maxNum2;
         }
         
    }
      //test the two maxes to find out the largest and retrun it
      
         
   //System.out.println(" The number of recursive calls is: " + recCount);
         if (maxNum < maxNum2)
         {
         return maxNum2;
         }
         else
         return maxNum;
  
         
 }
   public static void main (String[] args) throws IncorrectDataEntryException
   {
       int numOfData;
       int[] myArray;
       int first = 0;
       int maxNum;
       StringTokenizer myToken;
      String input;
       IncorrectDataEntryException problem = 
      new IncorrectDataEntryException ("Incorrect Data Input.  It's a WINDOWS world, " +
      "so look out your window while this program crashes!");
      try{
      do{
      System.out.println("Enter the amount of data to be processed: ");
      numOfData = Keyboard.readInt();
      if (numOfData == 0)
      throw problem;
      
      else
      myArray = new int[numOfData];
            
      System.out.print("Enter the data, allowing for a space between each line of entry");
      System.out.println(" (type -1 to exit program): ");
      input = Keyboard.readString();
      
      myToken = new StringTokenizer(input);
      
      for (int i = 0; i < numOfData; i++)
      {
         myArray[i] = Integer.parseInt(myToken.nextToken());
      }
      for (int i = 0; i < numOfData; i++)
      {
         System.out.println(myArray[i]);
      }
      maxNum = maxArray(myArray, first, numOfData -1);
      System.out.println ("maxnumber is: " + maxNum);
     }
     
        while (numOfData != -99999);
     }
     catch (NegativeArraySizeException exception)
     {
        System.out.println ("The program has ended");
     }
   
 
}
}

Originally posted by Anthony Villanueva:

If a non-final instance variable is not explicitly initialized it will have a default value. In the case of int, the default value is 0.
Can you post your code?

[Ron Newman]

You have another line of code in a block after a "return" statement. The code can never be executed.

[michael bradly]

Yeah, I kinda rigged the last return because I kept getting an error:
C:\JavaEx\entryTest\entryTest.java:8: missing return statement
{
and the only way to get it to compile and work was to put in the return for a max at the end.
I'm assuming there is an easier way?
Again, thanks for the help, Michael

Originally posted by Ron Newman:
You have another line of code in a block after a "return" statement. The code can never be executed.

[Ron Newman]

Every possible exit from your method has to return an int. No statement can directly follow a return statement.

[michael bradly]

Well, when I place it in front of the return statement I get the error that recCount may not have been initialized.

if (last == first)
      {  
         System.out.println("The number of rec calls is" + ++recCount);
         return anArray[0];
      } 

C:\JavaEx\entryTest\entryTest.java:27: variable recCount might not have been initialized
System.out.println("The number of rec calls is" + ++recCount);
So close yet so far, Michael

Originally posted by Ron Newman:
Every possible exit from your method has to return an int. No statement can directly follow a return statement.

[Anthony Villanueva]

Local variables must be explicitly initialized.

[michael bradly]

Although it is now noon, the thoughts never stop dawning upon me
I've deduced the problem I was having by switching all my variables to the class level. Now everything is working as I would like and my knowledge has increased.
Thank you Anthony and Ron..
Regards, Michael

Originally posted by Anthony Villanueva:
Local variables must be explicitly initialized.