Click here to watch in Youtube :
https://www.youtube.com/watch?v=P1BxbW8tv8M&list=UUhwKlOVR041tngjerWxVccw
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Java Tutorial: Generics in java | Java Generics [Upper bounded wildcard in Java Generics] |
import java.util.ArrayList; import java.util.List; public class GenericDemo1 { public static void main(String[] args) { List<Number> numberList= new ArrayList<Number>(); numberList.add(2.2); numberList.add(3.3); numberList.add(5.5); double sum = sum(numberList); System.out.println("sum = " + sum); List<Integer> integerList= new ArrayList<Integer>(); integerList.add(2); integerList.add(3); integerList.add(5); sum = sum(integerList); System.out.println("sum = " + sum); } public static double sum(List<Number> list) { double sum = 0; for (Number n : list) { sum += n.doubleValue(); } return sum; } }Output
Exception in thread "main" java.lang.Error: Unresolved compilation problem: The method sum(List<Number>) in the type GenericDemo1 is not applicable for the arguments (List<Integer>) at GenericDemo1.main(GenericDemo1.java:20)GenericDemo2.java
import java.util.ArrayList; import java.util.List; public class GenericDemo2 { public static void main(String[] args) { List<Number> numberList= new ArrayList<Number>(); numberList.add(2); numberList.add(3); numberList.add(5); double sum = sum(numberList); System.out.println("sum = " + sum); List<Integer> integerList= new ArrayList<Integer>(); integerList.add(20); integerList.add(33); integerList.add(50); sum = sum(integerList); System.out.println("sum = " + sum); } public static double sum(List<? extends Number> list) { double sum = 0; for (Number n : list) { sum += n.doubleValue(); } return sum; } }Output
sum = 10.0 sum = 103.0Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/GenericsDemo_upper_bounded_wildcard_App.zip?attredirects=0&d=1
Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/GenericsDemo_upper_bounded_wildcard_App
Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/539015917c8406e4be671410d713073b3971d1a5/BasicJava/GenericsDemo_upper_bounded_wildcard_App/?at=master
See also:
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