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 */