Java Exception as checked Exception但不需要在trycatch中抛出 [英] Java Exception as checked Exception but not required to be thrown in trycatch

问题描述

我有这个片段。

public final class StackOverflow{
   class MyException extends Throwable{
   }
   private void a(){
       try{
       }catch(MyException | Exception e){
       }
   }
}
exception StackOverflow.MyException is never thrown in body of corresponding try statement

我知道Exception正在扩展Throwable并且也是一个已检查的异常，MyException也在扩展Throwable，这也是一个已检查的异常！

I know that Exception is extending Throwable as well and also is a checked exception also MyException is extending Throwable which mades also a checked exception!

我的问题是为什么不需要在try catch中抛出Exception但MyException是什么？我认为这两个都是检查异常，这是差异？

My question is why Exception is not required to be thrown in the try catch but MyException is? I think that both are checked exception so which is the difference??

对不起，如果问题很简单。

Sorry if the question is simple.

推荐答案

Java语言规范（以粗体强调）：

这是一个编译时如果 catch 子句可以捕获已检查的异常类E1，则不会出现尝试 catch 子句的$ c>块可以抛出一个已检查的异常类，它是E1的子类或超类，除非E1是异常或超类异常。

It is a compile-time error if a catch clause can catch checked exception class E1 and it is not the case that the try block corresponding to the catch clause can throw a checked exception class that is a subclass or superclass of E1, unless E1 is Exception or a superclass of Exception.

我想这背后的基本原理是： MyException 确实是一个经过检查的例外。但是，未经检查的异常也会扩展异常（来自 RuntimeException 的传递继承），因此拥有 catch 包括异常类从编译器完成的异常分析中排除。

I guess the rationale behind this is that: MyException is indeed a checked exception. However, unchecked exceptions also extend Exception (transitive inheritance from RuntimeException), so having a catch include the Exception class is excluded from the exception analysis done by the compiler.

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