Java Learning--The handling of abnormal exception

* Second, how to deal with exception anomalies
* Java provides a catch-and-throw model of exception handling
* *. " Throw ": When we execute the code, when an exception occurs, an object of the corresponding exception type is generated at the code of the exception and
* throws this object. (Auto throw/manual throw)
* > Once the object of this exception class is thrown, the program terminates execution
* > The object of this exception class is thrown to the caller of the method.
* 2. " Catch ": Catch the object of the exception class thrown out of the previous step. How to catch? That is, the way the exception is handled
* Java provides two ways to handle an object of an exception class.
* The way of processing one:
* try{
*//code that may appear abnormal
*}catch (Exception1 E1) {
*//Way of handling 1
*}catch (Exception2 E2) {
*//Way of handling 2
*}finally{
*//code that must be executed
 *   }
* Note: variables declared in 1.try, similar to local variables, out of the try{} statement, cannot be called
* 2.finally is optional.
* Inside the 3.catch statement is the handling of the exception object:
* >getmessage (); Printstacktrace ();
* 4. There can be multiple catch statements, and the exception class object thrown in the try matches the type of the exception class in the catch, once it satisfies
* Executes the code in the catch. After execution, jump out of multiple catch statements
* 5. If the exception is handled, then the subsequent code continues to execute.
* 6. If multiple exception types in a catch are "side-by-side" relationships, you can either.
* If more than one exception type in a catch is a "containment" relationship, the subclass must be placed above the parent class for processing. otherwise error!
* 7.finally is stored in code that is bound to be executed, regardless of whether the exception is still unhandled in the try, catch, and if there is a return statement.
* 8.try-catch can be nested.
 *   
* Third, for run-time exceptions, can not be explicitly processed.
* For compile-time exceptions, you must explicitly handle them.

1 ImportJava.io.File;2 ImportJava.io.FileInputStream;3 Importjava.io.FileNotFoundException;4 Importjava.io.IOException;5 Importjava.util.Date;6 Importjava.util.InputMismatchException;7 ImportJava.util.Scanner;8 9 Importorg.junit.Test;Ten  One  A  Public classTestException1 { -     //compile-time exceptions - @Test the      Public voidTest6 () { -FileInputStream FIS =NULL; -         Try { -FIS =NewFileInputStream (NewFile ("Hello.txt")); +             intb; -              while((b = Fis.read ())! =-1) { +System.out.print ((Char) b); A             } at  -}Catch(FileNotFoundException E1) { -System.out.println ("The file can't be found!") "); -}Catch(IOException E1) { - System.out.println (E1.getmessage ()); -}finally { in             Try { - fis.close (); to}Catch(IOException e) { +                 //TODO auto-generated Catch block - e.printstacktrace (); the             } *         } $     }Panax Notoginseng  -     //Common run-time exceptions the     //4. Null pointer exception: Nullpointerexcetion + @Test A      Public voidTest5 () { the         //Person p = new Person (); +         //p = null; -         //System.out.println (p.tostring ()); $  $         Try { -String str =NewString ("AA"); -str =NULL; the System.out.println (Str.length ()); -}Catch(Exception e) {Wuyi             //e.printstacktrace (); theSystem.out.println ("An exception occurred with a null pointer"); -         } Wu     } -  About     //3. Type Conversion exception: ClassCastException $ @Test -      Public voidtest4 () { -         Try { -Object obj =NewDate (); AString str =(String) obj; +}Catch(classcastexception e) { theSYSTEM.OUT.PRINTLN ("Exception occurred with type conversion"); -             //System.out.println (10/0); $}Catch(Exception e) { the e.printstacktrace (); the}finally { theSystem.out.println ("Hello! beauty! "); the         } -         //String str1 = (string) new Date (); in     } the  the     //2. Arithmetic exception: ArithmeticException About @Test the      Public voidtest3 () { the         Try { the             inti = 10; +System.out.println (i/0); -}Catch(Exception e) { the             //e.printstacktrace ();Bayi System.out.println (E.getmessage ()); the         } the     } -  -     //1. Array subscript out-of-bounds exception: ArrayIndexOutOfBoundsException the @Test the      Public voidtest2 () { the         Try { the             int[] i =New int[10]; -             //System.out.println (i[10]); theSystem.out.println (i[-10]); the}Catch(Exception e) { theSystem.out.println ("There's an exception!" ");94         } the     } the  the @Test98      Public voidtest1 () { AboutScanner s =NewScanner (system.in); -         Try {101             inti =s.nextint ();102 System.out.println (i);103}Catch(inputmismatchexception e) {104System.out.println ("There is a type mismatch exception!") "); the         }106     }107}

Java Learning--The handling of abnormal exception