What is going wrong?

Frage zur Aufgabe

SimpleObject-Interface

Java Core, Level 3, Lektion 11

Gelöst

Seems that I dont understand the requirements correctly, so what needs to be changed?

1. Erstelle die Klasse StringObject.
2. Implementiere in der Klasse StringObject das SimpleObject-Interface mithilfe eines String-Parameters.
3. Das Programm muss sich kompilieren lassen.

Anforderungen:

Die Klasse StringObject muss das SimpleObject-Interface implementieren.
Das SimpleObject-Interface in der Klasse StringObject muss mit einem String-Parameter implementiert werden.
Die Klasse StringObject muss die getInstance-Methode des SimpleObject-Interfaces implementieren.
Die Solution-Klasse muss die Klasse StringObject besitzen.
Die Klasse StringObject muss static sein.

package de.codegym.task.task13.task1322; /* SimpleObject-Interface */ public class Solution { public static void main(String[] args) throws Exception { SimpleObject<String> stringObject = new StringObject(); } interface SimpleObject<T> { SimpleObject<String> getInstance(); } public static class StringObject implements SimpleObject{ public SimpleObject<String> getInstance(){ return null; } } }

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RFCO

Level 17 , Hanover, Germany

22 April 2020, 12:14

Ok... Just adding the required class which implements SimpleObject<String> is all... Too easy ;) interface SimpleObject<T> { SimpleObject<T> getInstance(); } public static class StringObject implements SimpleObject<String>{ public SimpleObject getInstance(){ return null; } }

Ivan

Level 22 , Nope, Bulgaria

25 März 2020, 18:19

Line 14, use <T> instead of <String> and line 17 StringObject<T>. Line 18 you may delete the <String> So, the <T> is a generic and can by of any type (string, integer, etc. - it parameterizes over types over). Here it is used to represent String (passes verification as T is a generic and can be accounts as for String and for others as well). So with the changes I suggested happens the following: Interface and its method will be a <T> type (String for this task) and the class will be implementing of type <T> (String for this task). It is hard to understand it at first, I know. I have forgotten it, so I hope it is somewhat helpful my explanation. Here is something to read: https://stackoverflow.com/questions/462297/how-to-use-classt-in-java https://docs.oracle.com/javase/tutorial/java/generics/types.html