Annotation format error, assertion error, ... , virtual machine error 不需要在 编译期检查的原因如下： error 随处都有可能发生，写出这些 error 会让程式码很杂乱，而且发生之後几乎不可 能修复。 Arithmetic exception, buffer overflow exception, ..., unsupported operation exception 不需要在编译期检查的原因如下： 一个正确的程式不会发生 runtime exception，写出这些 runtime exception 反而变成 一种累赘。 举例而言，在 circular data structure 永远都不该出现 null，但是错误的实作可能 会在执行的过程中抛出 NullPointerException，当 runtime exception 出现的同时， 通常代表程式写错了！ 其他 exception 都必须在编译期检查的原因如下： 即使是一个正确的程式，仍然会有例外发生，明确地写出哪些方法会抛出哪些例外，并 且写出这些例外要做什麽样的处理，整个错误处理程序可以提升系统的可靠度。 举例而言，sleep 方法很可能会被另一个执行绪以 interrupt 方法打断，此时 sleep 会抛出 interrupted exception 让对应的错误处理程序接手，进行适当的动作回应另一 个执行绪的中断行为。 回到问题原点：为什麽我特地把 sleep 重新包装成为一个只会抛出 runtime exception 的方法？ 原因是在某些正确实作的程式下，sleep 方法永远都不应该被 interrupted 。如果哪天 sleep 方法被 interrupted 那肯定是程式哪边写错了！ -- 以下是我的参考资料与节录部分内容 http://java.sun.com/docs/books/jls/third_edition/html/exceptions.html 11.2.4 Why Errors are Not Checked Those unchecked exception classes which are the error classes (Error and its subclasses) are exempted from compile-time checking because they can occur at many points in the program and recovery from them is difficult or impossible. A program declaring such exceptions would be cluttered, pointlessly. 11.2.5 Why Runtime Exceptions are Not Checked The runtime exception classes (RuntimeException and its subclasses) are exempted from compile-time checking because, in the judgment of the designers of the Java programming language, having to declare such exceptions would not aid significantly in establishing the correctness of programs. Many of the operations and constructs of the Java programming language can result in runtime exceptions. The information available to a compiler, and the level of analysis the compiler performs, are usually not sufficient to establish that such run-time exceptions cannot occur, even though this may be obvious to the programmer. Requiring such exception classes to be declared would simply be an irritation to programmers. For example, certain code might implement a circular data structure that, by construction, can never involve null references; the programmer can then be certain that a NullPointerException cannot occur, but it would be difficult for a compiler to prove it. The theorem-proving technology that is needed to establish such global properties of data structures is beyond the scope of this specification. --

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