Any help?

Question about the task

Under discussion

I've been stuck there for a while now trying to figure out what should be the utility class to call the method getDeclaredClasses on.

Class description:
1. It implements the List interface;
2. It is a private static class inside a popular utility class;
3. Accessing the list by index is not allowed. It throws an IndexOutOfBoundsException.
Using reflection (getDeclaredClasses method), return the appropriate type in the getExpectedClass method.

Requirements:

The getExpectedClass method must use the appropriate utility class's getDeclaredClasses method.
The getExpectedClass method must return the correct type.
The main method must call the getExpectedClass method.
The main method must display the returned class on the screen.

package com.codegym.task.task36.task3602; import java.util.*; /* Find the class by its description */ public class Solution { public static void main(String[] args) { /*for(Class clazz : Collections.class.getDeclaredClasses()){ System.out.println(clazz.getSimpleName()); }*/ System.out.println(getExpectedClass()); } public static <T extends List> Class<T> getExpectedClass() { String className = ""; Class clazz = null; Class<?>[] classes = Collections.class.getDeclaredClasses(); for (Class<?> c : classes){ try { List<String> list = (List)c.newInstance(); list.add("Test1"); list.add("Test2"); list.add("Test3"); list.get(1); } catch (InstantiationException | IllegalAccessException ignored){} catch (IndexOutOfBoundsException e){ className = c.getName(); break; } } try{ clazz = Class.forName(className); } catch (ClassNotFoundException ignored){} return clazz; } }

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Seb

Level 41 , Crefeld, Germany

23 February 2020, 12:29

Try to add further checks for a suitable class in the for loop, which is starting on line 21. Something like if (Modifier.isPrivate(c.getModifiers())) { // only private classes if (Modifier.isStatic(c.getModifiers())) { // only static classes if (List.class.isAssignableFrom(c)) { // only classes that implement the List interface // and then carry on in your try block I'm not entirely sure whether your try block will work out, if it does not, then first get a constructor for the c class using reflection.

Evghenii Seremet

Level 41 , London, United Kingdom

17 February 2020, 22:34

when you start the task you get Collections class already imported, which i believe is the utility class to use.