2017-02-02

java系列 - Error & Exception

definition

catch an error at compile time: before you even try to run the program (think in java)
-
java framework


Throwable─┬─Exception─┬─RuntimeException─┬─IndexOutOfBoundsException
          │           │                  ├─NullPointerException
          │           │                  │
          │           │                  │
          │           │                  │
          │           │                  │
          │           │                  │
          │           │                  │
          │           │                  └─
          │           │                  
          │           ├─ ReflectiveOperationException─┬─NoSuchMethodException
          │           │                               ├─ClassNotFoundException
          │           │                               └─IllegalAccessException
          │           │
          │           │
          │           │
          │           ├─IOException─┬─FileNotFoundException
          │           │             ├─EOFException
          │
          └─Error─┬─

	RuntimeException	non-RuntimeException
checked	×	√
occur in	runtime	runtime
must catch	×	√
caused by	programmer,such as NullPointerException, IndexOutOfBoundsException	external, such as FileNotFoundException
thrown	during the normal operation of JVM

Compile-Time Checking of Exceptions

设计思想

RuntimeException
一般情况下，不要捕获或声明RuntimeException。因为问题在于你的程序逻辑本身有问题，
如果你用异常流程处理了，反而让正常流程问题一直存在。
程序应该从逻辑角度尽可能避免这类异常的发生；

non-RuntimeException
RuntimeException之外的异常我们统称为非运行时异常。
从程序语法角度讲是必须进行处理的异常，如果不处理，程序就不能编译通过。

非运行时异常，编译期要做语法检查，即检查是否处理了catch。程序报Exception还是要运行期才能知道的。

An Exception is checked, and a RuntimeException is unchecked.

A checked exception must be handled explicitly by the code (catch or throw)
An un-checked exception does not need to be explicitly handled.

ambiguous, common errors, common misconceptions

Is non-RuntimeException CompiletimeException in java framework?
No, non-RuntimeException would be checked in compile time. But the Exception occurs in run time.

where did RuntimeException comes from

since JDK1.0

new/reasonable framework

In my view, the RuntimeException should be renamed as CheckedException

RuntimeException
- CheckedException
- UncheckedException
CompiletimeException
- ..

reference

《The Java™ Language Specification》11.2 Compile-Time Checking of Exceptions

other framework

Some programming languages and their implementations react to such errors
by peremptorily terminating the program; other programming languages allow an
implementation to react in an arbitrary or unpredictable way. Neither of these
approaches is compatible with the design goals of the Java SE platform: to provide
portability and robustness.

Instead, the Java programming language specifies that an exception will be thrown
when semantic constraints are violated and will cause a non-local transfer of control
from the point where the exception occurred to a point that can be specified by the
programmer.

python framework

reference: http://www.cnblogs.com/rubylouvre/archive/2011/06/22/2086644.html

Hexo