java异常捕获（5）自定义异常类

1. java中允许自定义异常类，以便对在程序的具体环境中出现的不符合特定而出现的异常进行处理，定义异常类的时候通常需要两个构造方法，一个无参，一个字符串为参数的构造方法，这个传入的字符串将用作就是getMessage所得到的描述信息，如果是Checded异常应当继承于Exception类，如果是Runtime异常应当继承于RuntimeException以下为代码示例

   package ThrowsAndThrowKeyWord;
   
   public class Throw1 {
   
       public static void main(String args[]){
           try{
               throwChecked(3);
           }catch (Exception e){
               System.out.println(e.getMessage());
           }
           throwRuntime(3);
       }
   
       public static void throwChecked(int a) throws Exception{
           if(a > 0){
               throw new DIYException("a不允许大于0");
           }
       }
       public static void throwRuntime(int a){
           if(a > 0){
               throw new DIYException2("a不允许大于0");
           }
       }
   }
   
   
   class DIYException extends Exception{
       public DIYException(){}
       public DIYException(String msg){
           super(msg);
       }
   }
   
   
   class DIYException2 extends RuntimeException{
       public DIYException2(){}
       public DIYException2(String msg){
           super(msg);
       }
   }