每天一點兒java---繼承exception類來實現自己的異常類

package prac_1;

/**
 * <p>Title: 捕獲異常和實現自己的異常類</p>
 * <p>Description: 通過繼承Exception類來實現自己的異常類。並使用try－catch來捕獲這個異常。</p>
 * <p>Copyright: Copyright (c) 2014</p>
 * <p>Filename: </p>
 * @author 王海濤
 * @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 {
/**
 *<br>方法說明：使用MyException類中默認的構造器
 */
  public static void a() throws MyException {
    System.out.println(
      "Throwing MyException from a()");
    throw new MyException();//拋出異常，結束方法
  }
/**
 *<br>方法說明：使用MyException類中帶信息的構造器
 */
  public static void b() throws MyException {
    System.out.println(
      "Throwing MyException from b()");
    throw new MyException("error in b ()");
  }
/**
 *<br>方法說明：使用了MyException中有編碼的構造器
 */
  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 :)