CODEWITHSUNDEEP
javasubclass
George Marin
George Marin

Reputation: 395

Why cant i change a subclass value

SO,letsay we have a bicycle superclass with cadence 0 and 3 subclasses.I want the "trotineta" sbuclass to have cadence 5 while the other 2 subclasses cadence remains 0. Why isnt this working?

    class Trotineta extends Bicycle{   
        Bicycle.cadence = 5;
    }

Upvotes: 0

Views: 63

Answers (3)

Ajit
Ajit

Reputation: 92

    class Bicycle{ 
                  int cadence = 0;
                  /* since no access modifier is mentioned, by default cadence becomes 
                  package private ie; it cannot be accessed outside the package 
                  in which it is defined now*/  
                 }

    class Trotineta extends Bicycle{
                                    Bicycle.cadence = 5; 
                                    /* you cannot do this as cadence is not a static 
                                    attribute of class Bicycle*/
                                    }

// Below is one of the possible solutions

   class Trotineta extends Bicycle{
             /*below code can also be written in a method but not outside as you have
               written in your example code*/
                                    { 
                                     this.cadence = 5; 
                                    //here 'this' is the current instance of Trotineta 
                                    } 
                                  }

Upvotes: 0

underwater ranged weapon
underwater ranged weapon

Reputation: 405

You can create getter and setter or just use word super

public class TestONE extends TestTWO {
    {
        super.gg = 4;
    }
    public static void main(String[] args) {
        System.err.println(new TestONE().gg);
    }
}
class TestTWO {
    static int gg = 0;
}

or 

public class TestONE extends TestTWO {
        public static void main(String[] args) {
            TestONE.setGg(5);
            System.err.println(new TestTWO().gg);
        }
    }
class TestTWO {
        protected static int gg = 0;

        public static int getGg() {
            return gg;
        }

        public static void setGg(int gg) {
            TestTWO.gg = gg;
        }   
    }

Upvotes: 1

Eran
Eran

Reputation: 393771

You haven't shown the definition of Bicycle.cadence, but based on the syntax, I'm assuming it's a static member. If you change a static member of the base class, all instances of all sub-classes will be affected by this change, since a static member has a single value for all instances of the class.

Now, if cadence wouldn't be static, you can give it a different value in the constructor of Trotineta (assuming the sub-class has access to that member).

public Trotineta ()
{
    cadence = 5;
}

This would be somewhat wasteful, though, since each instance of Bicycle would have its own cadence member.

Upvotes: 2

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