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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178
5
章
ヒューストンハーシー
※1
※3
、問題が発生しました
※3 訳注：ペンシルバニア州ハーシーは、有名なチョコレート HERSHEY'Sのメーカーの拠点です。
スレッドが問題
チョコレートボイラーの調子が悪いようです。典型的な Singleton を使ってコー
ドを改善したのですが、牛乳とチョコレートがすでに溶けているのに、どうい
うわけか ChocolateBoiler の fill() メソッドが動き出してしまったのです。あぁ、
2000リットルの牛乳（とチョコレート）が無駄になってしまいます！ 一体何が
起こったのでしょう！
どうなっているんだ！
新しい
Singleton
コードは正常に
動作していたのに。
1
つ考えられることは、チョコレート
ボイラーコントローラを最適化してマルチスレッドを利
用するようにしたことだけど。
ホットチョコレート
に注意してください
注意！
この問題の原因はスレッドの追加でしょうか。uniqueInstance
変数をChocolateBoilerのただ1 つのインスタンスに設定
したので、getInstance()のすべての呼び出しは同じインス
タンスを返すのではありませんか？
5
章
Singleton
パターン
you are here
179
2
つのスレッドそれぞれが、このコードを実行しています ...
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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.