在前一个catch块中处理的重新启动异常 [英] rethrowing exception handled in preceding catch block

问题描述

>）

详细来说，在Java SE 7及更高版本中，当您在catch子句中声明一个或多个
异常类型，并重新抛出由此catch块处理的
异常，编译器验证重新抛出异常的类型符合以下条件：

- try块能够抛出它。

- 没有其他可以处理的catch块。

- 它是一个catch子句的异常参数的子类型或超类型。

请注意第二点（

研究以下代码：

  static private void foo（）throws FileNotFoundException {
 try {
 throw new FileNotFoundException（）; 
} catch（FileNotFoundException e）{
 e.printStackTrace（）; 
} catch（IOException e）{
 throw e; 
} 
} 
  

此代码编译好。根据我的意见，在阅读上述文章的引用之后，我期望看到编译器将验证它，我会得到编译器错误。

我明白第二点错了吗？ >

解决方案

这是非常好的，因为 FileNotFoundException 是从 IOException ，并且因为您从不太具体到更具体的内容，不应该有任何问题。

---

编辑：

  static private void foo（）throws FileNotFoundException {
 try {
 throw新的FileNotFoundException（）; 
} catch（IOException e）{
 e.printStackTrace（）; 
} catch（FileNotFoundException e）{
 throw e; 
} 
} 
  

on oracle ofiicial site write (http://docs.oracle.com/javase/7/docs/technotes/guides/language/catch-multiple.html#rethrow)

In detail, in Java SE 7 and later, when you declare one or more exception types in a catch clause, and rethrow the exception handled by this catch block, the compiler verifies that the type of the rethrown exception meets the following conditions:

-The try block is able to throw it.

-There are no other preceding catch blocks that can handle it.

-It is a subtype or supertype of one of the catch clause's exception parameters.

Please concentrate on second point (There are no other preceding catch blocks that can handle it. )

Research following code:

static private void foo() throws FileNotFoundException  {
        try {
            throw new FileNotFoundException();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            throw e;
        }
    }

This code compiles good. According my opinion after reading quote from mentioned article I expect to see that compiler will verify it and I will get compiler error.

Did I understand second point wrong?

解决方案

This is perfectly fine because the FileNotFoundException is derived from IOException, and because you go from less specific to a more specific there should not be any issues.

---

edit:

static private void foo() throws FileNotFoundException  {
    try {
        throw new FileNotFoundException();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (FileNotFoundException e) {
        throw e;
    }
}

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