JAVA PROGRAM • LEVEL 11 — ABSTRACTION, INTERFACES & TYPE DESIGN
Implement an Abstract Class in Java
Learn implement an abstract class in java with a complete, compiler-ready Java 17 example.
PROBLEM UNDERSTANDING
Input and expected output
No input required
12.57
COMPLETE JAVA 17 PROGRAM
Complete Java 17 implementation
abstract class Shape { abstract double area(); } class Circle extends Shape { double r; Circle(double r){this.r=r;} double area(){return Math.PI*r*r;} }
class Main { public static void main(String[] args){System.out.printf("%.2f%n",new Circle(2).area());} }CURRENT STEP
Select Start to walk through the important lines.
SELECTED LINE
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EXPECTED OUTPUT FOR THE SAMPLE
12.57
PROGRAM EXPLANATION
Algorithm and explanation
- Initialize the deterministic sample values used for implement an abstract class in java.
- Create the required object and apply abstract class and Abstract method to its state or behavior.
- Print the final result and compare it with the documented sample output.
This Java 17 example demonstrates abstract class and Abstract method 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.
Create an object before accessing instance members; static members can be accessed through the class name.
Java is case-sensitive, and every statement that requires a semicolon must end with one.