Java Programming

I have a rather horribly written class, which I need to adapt. I could simply do this if I could override a method in one of it's inner classes. My plan then was to extend the original class, and override the method in question. But here I am struggling.

The code below is representative of my situation.

public class ClassA
{
    
   ValueChecks vc = null;
   
   /** Creates a new instance of Main */
   public ClassA()
   {
      System.out.println("ClassA Constructor");
           
      vc = new ValueChecks();
      
      vc.checkMaximum();
     
     // I want this to call the overridden method, but it does not, it seems to call
     // the method in this class. probably because vc belongs to this class
      this.vc.checkMinimum();
      
      this.myMethod();
      
   }
     
   
   protected void myMethod()
   {
      System.out.println("myMethod(SUPER)");
   }
   
   protected class ValueChecks
   {
      protected boolean checkMinimum()
      {
         System.out.println("ValueChecks.checkMinimum (SUPER)");
         return true;
      }
      protected boolean checkMaximum()
      {
         return false;
      }
   }
}

I have extended ClassA, call it ClassASub, and it is this Class which I instantiate. The constructor in ClassASub obviously calls the constructor in ClassA. I want to override the checkMinimum() method in ValueChecks, but the above code always calls the method in ClassA. The ClassASub code looks like this

public class ClassASub extends ClassA
{
   public ClassAInner cias;
  
   
   /** Creates a new instance of Main */
   public ClassASub()
   {   
      System.out.println("ClassASub Constructor");
   }
   
   
   protected void myMethod()
   {
      System.out.println("myMethod(SUB)");
   }

   protected class ValueChecks extends ClassA.ValueChecks
   {     
      protected boolean checkMinimum()
      {
         System.out.println("ValueChecks.checkMinimum (SUB)");
         return true;
      }
   }
   
}

The method myMethod seems to be suitably overridden, but I cannot override the checkMinimum() method.

I think this is a stupid problem to do with how the ValueChecks class is instantiated. I think I need to create an instance of ValueChecks in ClassASub, and pass a reference to it into ClassA. But this will upset the way ClassA works. Could somebody enlighten me please.