java - 是什么使得子类(即 RuntimeException 未被检查并且异常被检查)成为可能？

Question

是什么让编译器认为 RuntimeException 未被检查，尽管 RuntimeException 也是 Exception 类型。但是Exception是checked exception吗？

Answer 1

That is, the checked exception classes are Throwable and all its subclasses other than RuntimeException and its subclasses and Error and its subclasses.

^{JLS 11 > Exceptions > The Kinds of Exceptions}

这是规则，编译器知道它。给定异常是 RuntimeException 的子类这一事实(比方说 givenException instanceof RuntimeException)足以让编译器不将其视为检查异常。

The class RuntimeException is a direct subclass of Exception. RuntimeException is the superclass of all the exceptions which may be thrown for many reasons during expression evaluation, but from which recovery may still be possible.

RuntimeException and all its subclasses are, collectively, the run-time exception classes.

^{JLS 11 > Exceptions > The Kinds of Exceptions}