每天一点儿java---继承exception类来实现自己的异常类

package prac_1;

/**
 * 
Title: 捕获异常和实现自己的异常类
 * 
Description: 通过继承Exception类来实现自己的异常类。并使用try－catch来捕获这个异常。
 * 
Copyright: Copyright (c) 2014
 * 
Filename: 
 * @author 王海涛
 * @version 0.1
 */
class MyException extends Exception { 
  public MyException() {}
  public MyException(String msg) {
    super(msg);
  }
  public MyException(String msg, int x) {
    super(msg);
    i = x;
  }
  public int val() { return i; }
  private int i;
}

public class ExceptionDemo {
/**
 *
方法说明：使用MyException类中默认的构造器
 */
  public static void a() throws MyException {
    System.out.println(
      "Throwing MyException from a()");
    throw new MyException();//抛出异常，结束方法
  }
/**
 *
方法说明：使用MyException类中带信息的构造器
 */
  public static void b() throws MyException {
    System.out.println(
      "Throwing MyException from b()");
    throw new MyException("error in b ()");
  }
/**
 *
方法说明：使用了MyException中有编码的构造器
 */
  public static void c() throws MyException {
    System.out.println(
      "Throwing MyException from c()");
    throw new MyException(
      "error in c()", 404);
  }
  public static void main(String[] args) {
    try {
      a();
    } catch(MyException e) {
    	System.out.println( "Error="+e.getMessage());
    }
    try {
      b();
    } catch(MyException e) {
    System.out.println( "Error="+e.getMessage());
      //e.toString();
    }
    try {
      c();
    } catch(MyException e) {
    System.out.println( "Error="+e.getMessage());
      e.printStackTrace();
      System.out.println("error code: " + e.val());
    }
  }
} //end :)