An East Collection

EastCollection.java

package com.east;

import java.util.*;

interface ContainedListener {
    void notifyContained(Object item, boolean matched);
}

public class PermissionService implements ContainedListener {

    public static void main(String[] args) {
        new PermissionService().run();
    }

    private void run() {
        Permissions setA = new Permissions("A", "E", "I", "O", "U");
        Permissions setB = new Permissions("E", "O");
        setA.contains(setB, this);
    }

    @Override public void notifyContained(Object item, boolean contained) {
        if (contained)
            System.out.println("Contains: " + item);
    }

    private static class Permissions {

        private final List<Permission> contents = new ArrayList<>();

        public Permissions(String ... arguments) {
            for (String entry : arguments)
                add(createEntry(entry));
        }

        public void contains(Permissions toMatch, ContainedListener containedListener) {
            for (Permission permission : contents)
                toMatch.contains(permission, containedListener);
        }

        private void contains(Permission permission, ContainedListener containedListener) {
            containedListener.notifyContained(permission, contents.contains(permission));
        }

        private void add(Permission permission) {
            contents.add(permission);
        }

        private Permission createEntry(String value) {
            return new Permission(value);
        }
    }

    private static class Permission {

        private final String value;

        Permission(String value) {
            this.value = value;
        }

        public String toString() {
            return value;
        }

        public boolean equals(Object other) {
            return other instanceof Permission
                    && value.equals(((Permission) other).value);
        }
    }
}