异常处理示例,对于角标是整数不存在，可以用角标越界表示，

对于负数为角标的情况，准备用负数角标异常来表示。-Examples of Exception Handling.For the subscr ipt is an integer does not exist, you can use the subscr ipt out of range, said

For negative angular underlying case, ready to use negative subscr ipt exception to represent.