Double dnums[] = { 1.1, 2.2, 3.3, 4.4, 5.5 };
Stats<Double> dob = new Stats<Double>(dnums);
double w = dob.average();
System.out.println("dob average is " + w);
Float fnums[] = { 1.0F, 2.0F, 3.0F, 4.0F, 5.0F };
Stats<Float> fob = new Stats<Float>(fnums);
double x = fob.average();
System.out.println("fob average is " + x);
// See which arrays have same average.
System.out.print("Averages of iob and dob ");
if(iob.sameAvg(dob))
System.out.println("are the same.");
else
System.out.println("differ.");
System.out.print("Averages of iob and fob ");
if(iob.sameAvg(fob))
System.out.println("are the same.");
else
System.out.println("differ.");
}
}
The output is shown here:
iob average
is 3.0
dob average
is 3.3
fob average
is 3.0
Averages of
iob and dob differ.
Averages of
iob and fob are the same.
One last point: It is important to understand that the wildcard does not affect what type
of Stats objects can be created. This is governed by the extends clause in the Stats declaration.
The wildcard simply matches any valid Stats object.
Bounded Wildcards
Wildcard arguments can be bounded in much the same way that a type parameter can be
bounded. A bounded wildcard is especially important when you are creating a generic type
that will operate on a class hierarchy. To understand why, let's work through an example.
Consider the following hierarchy of classes that encapsulate coordinates:
// Two-dimensional coordinates.
class TwoD {
int x, y;
TwoD(int a, int b) {
x = a;
y = b;
}
}
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