oop - 编写一个包含它是实例化的类的单例是常规的吗？

Question

是否习惯性地编写一个包含它创建对象的类的单例，此外这个类包含一个私有构造函数，这样就不可能通过“new”关键字从这个类创建另一个对象？

package com.isi.core;

import com.isi.handlers.MouseMotionHandler;
import com.isi.states.MainMenuState;
import com.isi.states.PlayState;
import com.isi.uicomponents.Button;

import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

public class Singleton {

    private static MouseHandler instance = null;

    public static MouseHandler getInstance(Game game) {
        if (instance == null)
            instance = new MouseHandler(game);
        return instance;
    }

    public static class MouseHandler extends MouseAdapter {

        private Game game;

        private MouseHandler(Game game) {
            this.game = game;
        }

        public void mousePressed(MouseEvent e) {
            MouseMotionHandler mouseMotionHandler = game.getMouseMotionHandler();

            if (mouseMotionHandler.getOnComponent() != null && e.getButton() == 1 && mouseMotionHandler.getOnComponent() instanceof Button) {
                Button button = (Button) mouseMotionHandler.getOnComponent();

                if (game.getState() instanceof MainMenuState) {
                    if (button.getText().getString().equals("Play")) {
                        game.getGameStateManager().push(new PlayState(game));
                    } else if (button.getText().getString().equals("Exit")) {
                        System.exit(0);
                    }
                }
            }
        }

        public void mouseReleased(MouseEvent e) {

        }
    }
}

我创建了一个单例类，它返回从私有 MouseHandler 构造函数创建的单个 MouseHandler。

标签： oopdesign-patternssingletonsoftware-design