How check if array is full and if not full add to it?

I've got array. I've got a isFull method which checks if the array is full, but I don't know how to use this to check if it's full and if it's not full add to the array otherwise disregard the add call. The array should take 10 elements and then not accept any more, after this it should 'be full' and disregard any addSpy calls. How would you implement this?

public class ConcreteSubject extends AbstractSubject {

public int arySize;
private int i = 0;

private static AbstractSpy[] spies;

public ConcreteSubject(int a) {
    arySize = a;
    spies = new AbstractSpy[a];
}

@Override
public void addSpy(AbstractSpy spy) {
    if (spies.length < 10)
    {
        spies[i] = spy;
        System.out.println("spy added at index " + i);
        i++;
    }
}

public void isFull() {
    //1
boolean b = false;

for (int i = 0; i < spies.length; i++) {
    if (spies[i] == null) {
        b = true;
    }
}

if (!b) {
    System.out.println("Array is full");
}
else{
    System.out.println("Array not full");
}
}



public class TestSpies {

public static void main(String[] args) {

    ConcreteSubject cs = new ConcreteSubject(10);
    AbstractSpy spy = new ConcreteSpy();

    AbstractSpy[] spies = new AbstractSpy[10];

    cs.addSpy(spy);
    cs.addSpy(spy);
    cs.addSpy(spy);

    cs.isFull();

}
}