Security with Static Nested classes JAVA

Question

I was supposed to write this code so that ArrIg is a static nested class of Pair. However, I declared them as independent classes, but the code still ran as expected. I understand why it still ran.

I understand that static prevents the ArrIg object from being called once Pair is called(assuming ArrIg was a nested class of Pair). Further, this violated the syntax for static nested class, but it still worked. What are some of the dangers I have exposed this code to ?

public class ClassPair {

  public static void main(String[] args) {
    // TODO Auto-generated method stub

    int[] Ig= {1,2,3,4};
    Pair pair= ArrIg.minmax(Ig);

    System.out.print("min :"+pair.getFirst()+" | max :"+pair.getSecond());
  }

}


class Pair {
  public Pair(int a, int b){
    first=a;
    second=b;
  }

  public int getFirst(){
    return first;
  }
  public int getSecond(){
    return second;
  }

  private int first, second=0;    
}


class ArrIg{

  public static Pair minmax(int [] a){

    int min= a[0];//1
    int max=a[0];//1

    for(int i=0; i<a.length;i++){

      if (min>a[i]) min =a[i];//1
      if (max<a[i]) max=a[i];//2,3,4
    }

    return new Pair(min ,max);
  }

}

Answer 1

Access modifiers and nested classes are not a security mechanism. Indeed, it is pretty much trivial to circumvent them via reflection. (The only scenario where it might matter is if you are attempting to implement a system with a security sandbox.

The real purpose for access modifiers and nested classes is to provide encapsulation. It is about is about design leakage (unwanted dependencies) rather than information leakage and more general security concerns.

In this particular example, the (hypothethical) danger is that Pair could be instantiated and used outside of the ClassPair encapsulation. That could (hypothetically) be harmful, but for something like the Pair class allowing this could be a good thing.

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I would also add that you need to use the terminology properly if you want people to understand what you are saying. For instance "calling" an object is not meaningful. You call methods ... not objects.