List of protected nested class-CodePudding

I have a Java class with a nested protected class in it. In a method of another class (and in another package) I have to make a list of such nested protected type.

Is there a way to do this in Java?

// SomeClass.java
package stuff;

public class SomeClass {
  protected class Nested {
    int x;
    public Nested setX(int arg) {
      x = x;
      return this;
    }
    public int getX() {
      return x;
    }
  }

  public Nested make(int x) {
    return new Nested().setX(x);
  }
}

// MyClass.java
package project;

import java.util.List;
import java.util.ArrayList;
import stuff.SomeClass;

public class MyClass {
  public SomeClass instance;

  // I don't know what I should insert ...
  public List< /* ... here... */ ?> method() {
    var list = new ArrayList< /* ... and here... */ >();
    list.add(instance.make(1));
    list.add(instance.make(2));
    return list; // ... to return an ArrayList<SomeClass.Nested>
  }
}

Even some reflection magic would be ok for me

PS. I whuld not modify SomeClass

CodePudding user response：

You cannot, as Nested is not accessible outside of SomeClass. You can either make Nested public (or package-private if both SomeClass and MyClass are in the same package), or move MyClass inside of SomeClass.

CodePudding user response：

One solution is to create a public interface which Nested implements. Then you can refer to that interface type List<MyInterface>, for example. And make() returns the interface type, instead of Nested. This is the pattern used by many classes in the standard Java API.

CodePudding user response：

First of all you should know, that ther're static and not static inner classes.

Only one differenct: static class does not have a reference to it's parent class (but non static does). So it is not possible to create non static inner class without it's parent.

In case you want to have a list (e.g. Tree and Tree.Node), looks like you should create a static inner class.

Anyway, you can create a list of inner classes like List<[ParentClass].[InnerClass]> (you can have many . like List<A.B.C.D.E>).

public class MyClass {
  public SomeClass instance;

  public List<SomeClass.Nested> method() {
    List<SomeClass.Nested> list = new ArrayList<>();
    list.add(instance.make(1));
    list.add(instance.make(2));
    return list;
  }
}