読者です 読者をやめる 読者になる 読者になる

by shigemk2

当面は技術的なことしか書かない

イミュータブルなオブジェクトはスレッドセーフ

Scala プログラミング

ということ。中身が不変なので、マルチスレッド処理中にロックをかける必要がないから。

Immutable objects greatly simplify your program, since they:

  • are simple to construct, test, and use
  • are automatically thread-safe and have no synchronization issues
  • don't need a copy constructor
  • don't need an implementation of clone
  • allow hashCode to use lazy initialization, and to cache its return value
  • don't need to be copied defensively when used as a field
  • make good Map keys and Set elements (these objects must not change state while in the collection)
  • have their class invariant established once upon construction, and it never needs to be checked again
  • always have "failure atomicity" (a term used by Joshua Bloch): if an immutable object throws an exception, it's never left in an undesirable or indeterminate state

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