|
|
Optimize with a SATA RAID Storage Solution
Range of capacities as low as $1250 per TB. Ideal if you currently rely on servers/disks/JBODs
Page 6 of 10
class Super
{
double x = 2;
void draw ()
{
System.out.println ("Super");
}
}
class Sub extends Super
{
double x = 3;
void draw ()
{
System.out.println ("Sub");
System.out.println ("x = " + x);
System.out.println ("super.x = " + super.x); // Access the superclass x field.
super.draw (); // Call the superclass draw() method.
}
}
The code fragment above reveals another use for the super keyword. Prefixing super. to either a field name or a method call results in the superclass field being accessed or the superclass method being called.
If you were to execute new Sub ().draw (); against the above code fragment, the following would print:
Sub x = 3.0 super.x = 2.0 Super
Suppose that, in the Circle and Sub classes in the code fragments above, you declare the draw() method private -- as in private void draw(). If you do that and then execute the code, the compiler will report an error because you cannot make a field or method's
accessibility more restrictive in a subclass.
A subclass method can only override a superclass method if the superclass method is both accessible and nonfinal. You declare
a final method by using the final keyword. For example, suppose Super declares draw() as follows: final void draw () { System.out.println ("Super"); }. Attempting to compile the above code fragment with the newly marked final draw() method results in a compiler error.