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程式語言概念-設計模式-單例模式

程式語言概念
設計模式
單例模式

讓程式在執行的時候，在記憶體中，只存在唯一一個實作物件，後面再被實作出來也只是再次呼叫該物件而已，在設計單利模式，有幾個注意點，執行緒安全、lazy初始化，以下六種。

  1. Lazy初始化，指行緒不安全
  2. Lazy初始化，執行緒安全
  3. 沒Lazy初始化，指行緒安全
  4. 登記式
  5. 雙重校驗檢索
  6. 枚舉法
Lazy初始化：在類別定義中，判斷物件是否實作，如否則實作物件。
執行緒安全：會針對執行緒進行lock的動作。
登記式：難以說明
雙重校驗：對於是否實作物件檢查兩次，以避免重複實作物件。
枚舉法：難以說明

最常用的方法，第三種。

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