get method returns null array when invoked form anther class . It results nullPointerException

Question

I keep getting NullPointerException when I try to access array elements from another class using the get method. My code uses a constructor to initialize the array, and it works just fine.

MagazineValue.class

public class MagazineValue {

public MagazineValue(){
}
private String[]magazineName;
public MagazineValue(String[] magazineName){


    this.magazineName = new String[magazineName.length];
    System.arraycopy(magazineName, 0, this.magazineName, 0,
    magazineName.length);

}

public String[] getMagazineName(){
    return magazineName;
}
}

The constructor here copy's array value from the argument to a private array variable. When I try to invoke getMagazineName() from another class, it shows that the array is still null. Is there any way I can solve this? It sure seems easy but it took me a lot of time.

FirebaseValueListner.class

public class FirebaseValueListner {
public void setMagazineName(){
    String[]magazineName={"African Daily" , "African Bussines", "African Women"};
    MagazineValue setValue= new MagazineValue(magazineName);
}

}

The FirebaseValueListner gets values from the Firebase database and saves it values to an ArrayList and later copy's the values to arrays. The arrays are passed to the constructor of the MagazineValues.

LibraryFragment.class `

public class LibraryFragment {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    String[]magazineName;
    MagazineValue getMagazineName;
    getMagazineName=new MagazineValue();

    magazineName=getMagazineName.getMagazineName();
    System.out.println("Magazine Name : " +magazineName[1]);


      }

    }

`

with this code you posted is that beh not possible.. you are doing ***this.magazineName = new String[magazineName.length];*** so magazine can not be null — ΦXocę 웃 Пepeúpa ツ, Jun 24 '17 at 20:54
Can you please share your code how you are calling this method from other class — gati sahu, Jun 24 '17 at 20:55
btw an array pointing to null ref is totally diff to an array holding objects pointing to null.... are you aware of that?? — ΦXocę 웃 Пepeúpa ツ, Jun 24 '17 at 20:55
This is not an MCVE, I can't run this myself and reproduce the error. The idea is to start again with a test project and write a minimal amount of code that produces the error. Any way, you're creating a `MagazineValue` here, but not doing anything with it. — Jorn Vernee, Jun 24 '17 at 21:23

score 0 · Answer 1 · answered Jun 24 '17 at 21:41

0

You must have defined a constructor with no arguments. Because you write getValue = new MagazineValue(); It may not initialize the field magazineName.

answered Jun 24 '17 at 21:41

I already did that, must have forgotten to put it there. – Nathan Damtew Jun 24 '17 at 21:43
@NathanDamtew The fact that you use the default constructor is the problem here. You don't initialize the array in the default constructor. – Jorn Vernee Jun 24 '17 at 22:13

get method returns null array when invoked form anther class . It results nullPointerException

1 Answers1