[读书笔记]about Exceptions

 

Ø        Exceptions identify errors that arise in your program.

Ø        Exceptions are objects of subclasses of the Throwable class.

Ø        Java includes a set of standard exceptions that may be thrown automatically, as　a result of errors　in your code, or may be thrown by methods in the standard classes in Java.

Ø        If a method throws exceptions that aren’t caught, and aren’t represented by subclasses of the　Error class or by subclasses of the RuntimeException class, then you must identify the exception　classes in a throws clause in the method definition.(也就是说，Error和RuntimeException的子类是不需要捕获的；而其它种类的Exception被编译器强制要求捕获处理。)

Ø        If you want to handle an exception in a method, you must place the code that may generate the　exception in a try block. A method may have several try blocks.

Ø        Exception handling code is placed in a catch block that immediately follows the try block that　contains the code that can throw the exception. A try block can have multiple catch blocks　that each deals with a different type of exception.

Ø        A finally block is used to contain code that must be executed after the execution of a try　block, regardless of how the try block execution ends. A finally block will always be executed　before execution of the method ends.

Ø        You can throw an exception by using a throw statement. You can throw an exception anywhere　in a method. You can also rethrow an existing exception in a catch block to pass it to the calling　method.

Ø        You can define your own exception classes that, in general, should be derived from the class　Exception.