1 package p1.exception;
 2 
 3 
 4 /*
 5  * 异常处理的捕捉形式:
 6  * 这是可以对异常进行针对性处理的方式.
 7  * 
 8  * 具体格式是:
 9  * try{ 
10  *        //需要被检测异常的代码
11  * }
12  * catch(异常类 变量){ //该变量用于接收发生的异常对象
13  *         //处理异常的代码
14  * }
15  * finally{
16  *         //一定会被执行的代码
17  * }
18  */
19 class FuShuIndexException extends RuntimeException /*Exception*/{//可以改继承运行异常，就不会报编译错误
20     public FuShuIndexException() {
21         // TODO Auto-generated constructor stub
22     }
23     
24     FuShuIndexException(String msg){
25         super(msg);
26     }
27 }
28 class Demo {
29     public static int method(int[] arr,int index) throws NullPointerException, FuShuIndexException {
30         
31         if (arr == null) {
32             throw new NullPointerException("没有任何数组实体");
33         }
34         if (index<0) {
35             throw new FuShuIndexException("角标变成负数了");
36         }
37         return arr[index];
38     }
39 
40 }
41 
42 public class ExceptionDemo4 {
43 
44     public static void main(String[] args) {
45 
46         int[] arr = new int[3];        
47         Demo d = new Demo();
48         try {
49 //            int num = d.method(arr,0);
50             int num = d.method(null,-30);
51             System.out.println("num="+num);
52         } catch (FuShuIndexException e) {
53             // TODO: handle exception
54             System.out.println("message:"+e.getMessage());//message:角标变成负数了
55             System.out.println("string:"+e/*.toString() 输出语句后输出都会变成字符串*/);//string:p1.exception.FuShuIndexException: 角标变成负数了
56             e.printStackTrace();//jvm默认的异常处理机制就是调用异常对象的该方法
57             System.out.println("负数角标异常");
58         } catch (NullPointerException e) {
59             // TODO: handle exception
60             System.out.println(e.toString());
61         }/*catch(Exception e) {//多catch时父类的catch放在最下面，否则编译失败
62             
63         }*/
64         
65         
66         System.out.println("over");
67         
68     }
69     
70 }
71 /*
72 log4j  log for (java; ;) {
73 
74 }
75 */

ExceptionDemo4