Класс для генерации клавиатуры бота ВКонтакте. Пример того, как не нужно делать.

Keyboard.java

/*
Пример того, как делать не нужно.
Работает и пофиг!
*/

import com.google.gson.Gson;
import com.google.gson.JsonObject;

import java.util.ArrayList;

public class Keyboard{

    private boolean one_time;
    private ArrayList<ArrayList<Button>> buttons = new ArrayList<>();
    private int row = 0;

    public Keyboard(boolean one_time){
        this.one_time = one_time;

        this.buttons.add(new ArrayList<>());
    }

    public Keyboard addButton(Button button){
        return this.addButton(button, false);
    }

    public Keyboard addButton(Button button, boolean new_line){
        if(new_line){
            this.row += 1;
            this.buttons.add(new ArrayList<>());
        }

        this.buttons.get(this.row).add(button);

        return this;
    }

    @Override
    public String toString(){
        Gson gson = new Gson();
        JsonObject json = new JsonObject();
        json.addProperty("one_time", this.one_time);
        json.add("buttons", gson.toJsonTree(buttons));

        return json.toString();
    }

    public static class Button{

        public final static String COLOR_PRIMARY = "primary";
        public final static String COLOR_DEFAULT = "default";
        public final static String COLOR_NEGATIVE = "negative";
        public final static String COLOR_POSITIVE = "positive";

        private Action action;
        private String color;

        public Button(Action action, String color){
            this.action = action;
            this.color = color;
        }

        public Action getAction(){
            return action;
        }

        public String getColor(){
            return color;
        }

        public static class Action{

            private String type = "text";
            private String payload;
            private String label;

            public Action(Payload payload, String label){
                this.payload = payload.toString();
                this.label = label;
            }

            public String getType(){
                return type;
            }

            public String getPayload(){
                return payload;
            }

            public String getLabel(){
                return label;
            }

            public static class Payload{

                private String command;

                public Payload(String command){
                    this.command = command;
                }

                public String getCommand(){
                    return command;
                }

                @Override
                public String toString(){
                    JsonObject json = new JsonObject();
                    json.addProperty("command", this.command);

                    return json.toString();
                }
            }
        }
    }
}