Mega Code Archive
Using Bounded Wildcards in Methods
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The syntax for using an upper bound is as follows:
GenericType<? extends upperBoundType>
import java.util.ArrayList;
import java.util.List;
public class MainClass {
public static double getAverage(List<? extends Number> numberList) {
double total = 0.0;
for (Number number : numberList) {
total += number.doubleValue();
}
return total / numberList.size();
}
public static void main(String[] args) {
List<Integer> integerList = new ArrayList<Integer>();
integerList.add(3);
integerList.add(30);
integerList.add(300);
System.out.println(getAverage(integerList)); // 111.0
List<Double> doubleList = new ArrayList<Double>();
doubleList.add(3.0);
doubleList.add(33.0);
System.out.println(getAverage(doubleList)); // 18.0
}
}
111.0
18.0
]]>