June 2022
Beginner to intermediate
672 pages
17h 23m
Japanese
Content preview from Head Firstデザインパターン 第2版 ―頭とからだで覚えるデザインパターンの基本
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384
10
章
状態マシンの復習
状態マシンの基礎
25
セントを投入する
25
セントを取り出す
ハンドルを回す
これらのアクションは、ガム
ボールマシンのインタフェー
ス（ガムボールマシンで実行
できること）です。
どのようにして、この状態図から実際のコードを作成していけばよいでしょう
か？
状態マシンを実装するための概要を示します。
まず状態を集める。
1
ガムボール
販売
25
セント
未受領
25
セント
受領
ガムボール
なし
これらは状態です。全部で
4
つです。
次に、現在の状態を保持するためのインスタンス変数を作成し、状態ごとの値を定義する。
2
final static int SOLD_OUT = 0;
final static int NO_QUARTER = 1;
final static int HAS_QUARTER = 2;
final static int SOLD = 3;
int state = SOLD_OUT;
一意な整数で表現された各状態。
訳注：米国の
25
セント硬貨は
Quarter
と呼ばれています。
現在の状態を保持するインスタンス変数です。最初に
箱から取り出して電源スイッチを入れたときには、マ
シンは空の状態なので、この変数を「売り切れ」に設
定します。
次に、このシステムで起こり得るすべてのアクションを集める。
3
図を見ると、どのアクションを行っても
状態が遷移します。
ガムボールを出す
「ガムボールを出す」は、どちらかとい
うとマシンがマシン自身に対して行う内
部アクションです。
「ガムボールなし」は短く「売り切れ」 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.