Exception handling mechanism for Java

At least in my existing learning stage, for the exception, in the actual project is not how to use, including some PHP projects, is also not used, perhaps in one aspect, my code is still not very mature. However, I still have to, in the primary stage of learning or should be functional-oriented, and then to consider the rigor of the code.
The exception handling mechanism is the three aspects of getting exceptions, handling exceptions, and throwing exceptions.

 PackageYichang;ImportJava.beans.Expression;Importjava.io.*;Importjava.net.*; Public  class yichang_1 {    /** * @param args * *     Public Static void Main(string[] args) {FileReader p=NULL;Try{p =NewFileReader ("F:\\a1.txt"); }Catch(FileNotFoundException e) {//TODO auto-generated catch blockE.printstacktrace (); }finally{//There are no exceptions to be performed, generally such as resources to be closed            if(p!=NULL){Try{P.close (); }Catch(Exception E2) {//Todo:handle exceptionSystem.out.print ("Resource not closed"); }            }        }    }}

 PackageYichang;ImportJava.io.filereader;public class yingyang2 {    /** * @param args * *public static void Main (string[] args)throwsexception{//TODO auto-generated method stubB1 m1=NewB1 ();    M1.open_file (); }} class B1 extends A1{} class A1{int A; public void Open_file ()throwsexception{FileReader p =NewFileReader ("F://a.txt"); }}

Exception handling mechanism for Java