Java Object-oriented sixth chapter

First, abnormal

1. What is an exception?

Exceptions to Java programs that occur during operation

2, how to do exception handling in Java?

exception handling Mechanisms in Java

Try, catch, finally, throw, throws

try{

Code with the possibility of an exception

}catch (Exception type) {

Capturing and handling exceptions that occur

Return

System.exit (1);//finally statement block will not execute

}finally{

Code to execute regardless of whether the program has an exception

｝

Try...catch...finally altogether there are 3 combinations of methods

Try...catch ... (Catch can be many, but be aware of the order of subclasses stepfather classes first)

Try...catch...finally ...

Try...finally ....

 Public classTest3 {Private StaticLogger Logger=logger.getlogger (Test3.class. GetName ());  Public Static voidmain (String [] args) {Scanner input=NewScanner (System.inch); System. out. Print ("Please enter dividend:"); intnum1=Input.nextint (); System. out. println (""); System. out. Print ("Please enter a divisor:"); intNum2=Input.nextint (); Try{System. out. println (num1/num2); System. out. println ("Thanks for using this program! "); }Catch(inputmismatchexception e) {logger.error ("An error has occurred! Divisor and dividend must be integers! ", E); }Catch(ArithmeticException e) {logger.error (E.getmessage ()); }Catch(Exception e) {logger.error (E.getmessage ()); }finally{System. out. println ("Happy Drink You use this program! "); } }} example

Example

3. What are the common types of exceptions? Table 6-1

4. Throw and THROWS2 keywords are all used to throw an exception

The difference has 3 points, P149 page

Different roles

Different locations

Content is different,

Ii. Log4j:1 Open Source Logging tool

Steps to use:

1. Add the log4j. jar file to the project

2. Create log4j.propterties file "Save log information Related Settings"

3. writing configuration information for logs "output level, destination, format"

4, in the program, using log4j logging (SQL log, Exception Log, business log and other 3 types of log information)

Java Object-oriented sixth chapter