package com.crawler.command; import java.util.ArrayList; import java.util.List; public class CommandHistory { private static CommandHistory instance; private List history; private CommandHistory() { history = new ArrayList<>(); } public static CommandHistory getInstance() { if (instance == null) { instance = new CommandHistory(); } return instance; } public void add(String command) { history.add(command); } public List getHistory() { return new ArrayList<>(history); } public void clear() { history.clear(); } public int size() { return history.size(); } }