Unable to access my constant/final String array values declared in a Java interface

Question

So I have an interface, it's got a few constant integers declared and I can access these in any class which implements said interface.

I just declared an array of constant strings in the interface, and I tried to access it, resulting in a null pointer expression, my array is declared like so:

public static final String[] STRINGS = {"bla","bla","bla","bla", "bla", "bla"};

In the test program, the following line returns a NullPointerException:

System.out.println(STRINGS[1]);

So, my question: Is there any problem here, or can you only work with integer constants in an interface?

public class MyFrame extends JFrame implements MyInterface {
....
....
private static JCheckBox[] checkBoxes = new JCheckBox[NUMBER];
....
....
int counter = 0;
        for (JCheckBox box : checkBoxes) {
            box.setText(STRINGS[counter]);
            box.setSelected(false);
            checkBoxPane.add(box);
            counter++;
        }

 ....

The above code shows the test class, NUMBER and STRINGS are declared in MyInterface, I've changed the names for simplicity.

Thanks in advance.

Answer 1

Elements in an Object array are null by default. Ensure that each JCheckBox is initialized before attempting to invoke a method on the component

for (int i=0; i < checkBoxes.length; i++) {
    checkBoxes[i] = new JCheckBox();
}

Answer 2

This woks perfectly ok.

public interface Trail {
    public static final String[] STRINGS = {"bla","bla","bla","bla", "bla", "bla"};
}

Implementation

public class X implements Trail{
    public void get() {
        System.out.println(STRINGS[1]);
    }
}

public class TEstMain {
public static void main(String[] args) {

    X x = new X();
    x.get();
}

Output:

bla