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Java Java Objects (Retired) Harnessing the Power of Objects Method Signatures

Adam Brown
Adam Brown
1,893 Points

Why does while (dispenser.dispense()) { System.out.println("Chomp!"); } actually cause the dispenser to dispense?

My understanding of while() is that it is stating while "this" is true, this will happen. I don't understand how this line of code actually will make pez dispense. I would understand if it were something like while(mPezCount>0){dispenser.dispense();}, but just don't see how putting something in the while parentheses calls for an action to take place. Does it have something to do with it being a boolean statement?

1 Answer

Christopher Augg
Christopher Augg
21,223 Points

Adam,

Yes, it does have to do with it being a boolean statement. The dispense() method can be called like this as long as it returns a boolean.

The dispense method returns a boolean.

       public static boolean despense() {

        //initializes to false
         boolean wasDispensed = false; 

        //calls isEmpty() to make sure it is not empty using !
        if(!isEmpty()) {
            // Only decrements if mPezCount is not empty
            mPezCount--;        
            // Only assigns true if mPezCount is not empty. 
            wasDispensed = true; 
        }
        // Returns false if mPezCount is empty. Returns true if mPezCount is not empty.
        return wasDispensed;
    }

         // On each iteration- if dispense() returns true (not empty), execute inner block.
         //                    if dispense() returns false(is empty), break out of while loop. 
         while (dispenser.dispense()) { 
               System.out.println("Chomp!"); 
         }

Basically, the while statement reads : I will continuously call the dispense() method and execute the code within its block as long as the Pez dispenser is not empty.

I hope this helps.

Regards,

Chris