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Java Java Objects (Retired) Harnessing the Power of Objects Incrementing and Decrementing

Posted by Ivan Yudhi
Ivan Yudhi
2,031 Points

How does boolean work?

So I'm trying to get a better understanding of how boolean works

for the method below..

public boolean isEmpty() {                                                                      
        return mPezCount == 0;
    }

If my understanding is correct, it's basically saying: if mPezCount is equal to 0, return boolean value TRUE. if mPezCount is not equal to 0, it will return false.

But when I try the following code on Example.java (and considering mPezCount is set to 0 in constructor)

public class Example {

    public static void main(String[] args) {

      System.out.println("We are making a new Pez Dispenser");
      PezDispenser dispenser = new PezDispenser("Donatello");                                                               
      String str = Boolean.toString(dispenser.isEmpty()); //trying to convert boolean to string
      System.out.printf(str);

    }
}

Isn't this supposed to print "TRUE"? I'm actually getting something else.. and this made me think about how boolean actually work.

Thanks!

2 Answers

Yonatan Schultz
Yonatan Schultz
12,045 Points
Yonatan Schultz
Yonatan Schultz
12,045 Points

Your understanding is fine as I read it. I think the issue is with your String str = Boolean.toString line.

If you want to create a String with the value of your boolean dispenser.isEmpty() I think you want to use:

String.valueOf(dispenser.isEmpty());

As per the String class documentation here:

http://docs.oracle.com/javase/7/docs/api/java/lang/String.html

Apoorva Shukla
Apoorva Shukla
9,138 Points
Apoorva Shukla
Apoorva Shukla
9,138 Points

Hi Ivan,

I tried Boolean.toString() function in my code and it is working fine. Have you declared mPezCount = 0 in your constructor method. My code is:

public class Example {

public static void main(String[] args) {
    // Your amazing code goes here...
    System.out.println("We are a making a new Pez Dispenser.");
    PezDispenser dispenser = new PezDispenser();
    String str = Boolean.toString(dispenser.isEmpty());
    System.out.printf("Is dispenser empty: %s\n",
                      str);
}

}

This is my constructor method: public PezDispenser(){ mPezCount = 0; }

This is my isEmpty method: public boolean isEmpty(){ return mPezCount == 0; }

May be this code will provide some help to you

Thanks!