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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世の中の
Observer
パターンを調べる
Observer
パターンは最もよく使われるパターンの
1
つで、多くのライブラリやフレームワー
クでよく使われています。例えば、
JDK
（
Java Development Kit
）では
JavaBeans
と
Swing
ラ
イブラリはどちらも
Observer
パターンを利用しています。
Observer
パターンは
Java
に限った
ものでもありません。他の例を挙げると、
JavaScript
のイベント、
Cocoa
、
Swift
の
KVO
（
Key-
Value Observing
）プロトコルでも使われています。デザインパターンを知っていることの利
点の
1
つは、お気に入りのライブラリの設計の背後にある動機を認識し、すぐに理解できる
ことです。
Swing
ライブラリを簡単に調べ、
Observer
パターンをどのように使っているか確
認してみましょう。
Swing
ライブラリ
Swing
は
Java
のユーザインタフェース用の
GUI
ツールキットであることはご存知だと思い
ます。
Swing
の最も基本的なコンポーネントの
1
つが
JButton
クラスです。
JButton
のスーパー
クラス
AbstractButton
を調べると、リスナを追加
/
削除する多数のメソッドがあるのがわかり
ます。これらのメソッドは、オブザーバの追加や削除を実行できます。
Swing
ではオブザー
バはリスナと呼ばれ、
Swing
コンポーネントで発生したさまざまな種類のイベントを監視し
ます。例えば、
ActionListener
は、ボタンで発生する可能性のあるあらゆる種類の動作（ボタ ...
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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.