JAVA PROGRAM • LEVEL 13 — COLLECTIONS & GENERICS
Use a Bounded Wildcard in Java
Learn use a bounded wildcard in java with a complete, compiler-ready Java 17 example.
PROBLEM UNDERSTANDING
Input and expected output
No input required
12.0
COMPLETE JAVA 17 PROGRAM
Complete Java 17 implementation
import java.util.*;
class Main{static double sum(List<? extends Number> values){double total=0;for(Number value:values)total+=value.doubleValue();return total;}public static void main(String[] args){System.out.println(sum(List.of(2,4,6)));}}CURRENT STEP
Select Start to walk through the important lines.
SELECTED LINE
No line selected
EXPECTED OUTPUT FOR THE SAMPLE
12.0
PROGRAM EXPLANATION
Algorithm and explanation
- Initialize the deterministic sample values used for use a bounded wildcard in java.
- Apply ? extends Number and Wildcard in the order shown by the program.
- Print the final result and compare it with the documented sample output.
This Java 17 example demonstrates ? extends Number and Wildcard through a complete, executable program. The values are intentionally small so students can trace each statement, verify the output, and then modify the example safely in the online compiler.
EFFICIENCY
Time and space complexity
O(1)
O(1)
DEBUGGING CHECKLIST
Common mistakes
Keep the class name Main and the entry method signature public static void main(String[] args) when using the online compiler.
Check the loop boundary and update expression carefully to avoid skipping the final value or creating an infinite loop.
Java is case-sensitive, and every statement that requires a semicolon must end with one.