@Gui.CollapsibleObject
    public ArrayList<Group> groups = new ArrayList<Group>();

package in.techpro424.groupmessages.config;

import java.util.ArrayList;

public class Group {
    String name =  "group1";
    public ArrayList<String> playerNames = new ArrayList<String>();

    public Group(String name, ArrayList<String> arrayList) {
        this.name = name;
        this.playerNames = arrayList;
    }
}