Java exception -- runtimeexception and user define exception

1. runtimeexception

I was asked about the difference between exception and runtimeexception when I was asked about Morgan it today. I couldn't answer the question at that time. I 'd like to know about it later.

First, take a lookCodeThe main content is to convert a string-type number into an integer number and then multiply the two numbers. The Code is as follows:

View code

Public ClassRuntimeexception {Public Static VoidMain (string [] ARGs ){//Todo auto-generated method stubString STR = "123";IntTemp =Integer. parseint (STR); system. Out. println (temp*Temp );}}
 

ViewSource codeAs follows:

View code

Public Static IntParseint (string S)ThrowsNumberformatexception {ReturnParseint (s, 10);}
 

We found that the numberformatexception was thrown in this method, but we didn't find try... catch in the above Code to handle it. Why.According to our knowledge about exception handling, if an exception is thrown through throws, try... catch, but there must be try... catch.

Next we will observe the inheritance relationship of the numberformatexception class:

We can find that numberformatexception is a subclass of runtimeexception, so we need to understand the concepts of exception and runtimeexception:

1. Exception: InProgramTry... catch must be used for processing.
2. Runtimeexception: Try... catch is not used for processing. However, if an exception is generated, the exception will be handled by JVM.

The exception handling mechanism is also recommended for subclasses of runtimeexception. Although the exception of runtimeexception does not support try... if an exception occurs, the program will be interrupted. Therefore, to ensure that the program can still be executed after an error occurs, try... catch exception handling mechanism.

 

2. user defined exception

The following is an example of a custom exception:

View code

 Class Myexception Extends  Exception {  Public  Myexception (string MSG ){  Super (MSG );}}  Public   Class  Defaultexception {  /**  *  @ Param  ARGs  */      Public   Static   Void  Main (string [] ARGs ){  //  Todo auto-generated method stub          Try {  Throw   New Myexception ("custom exception" );}  Catch  (Exception e) {system. Out. println (E );  //  Edu. SJTU. Ist. comutil. myexception: custom exception  //  System. Err. println (E );  //  E. printstacktrace ();  // Stacktraceelement [] STS = E. getstacktrace ();  //  For (stacktraceelement ST: STS ){  //  System. Err. println (ST );  //  }  //  System. Err. println (E. getstacktrace ());  }}} 

Output result:

Myexception: custom exception