問(wèn)題描述
我只是想知道...
為什么我只能有一個(gè) Calendar 對(duì)象的實(shí)例.有沒(méi)有理由讓它成為單身人士?
why can i have only one instance of Calendar object. Is there a reason for it to be a singleton?
我已嘗試閱讀 文檔 但他們沒(méi)有提到為什么需要這樣做.快速谷歌搜索沒(méi)有給我任何答案.
I have tried to read the documentation but they didn't mention why this is needed. And a quick google search didn't give me any answers.
推薦答案
Calendar 不是單例，它是一個(gè)抽象類(lèi).getInstance 方法是一個(gè)工廠方法，它返回 Calendar 類(lèi)的具體實(shí)現(xiàn).
Calendar is not a singleton, it is an abstract class. The getInstance method is a Factory method that returns a concrete implementation of the Calendar class.
在 Google 上搜索 java.util.Calendar 源代碼，您將了解它是如何工作的.
Search Google for java.util.Calendar source code, and you will see how it works.
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