什么情况要抛出异常
怎样抛出异常
import java.util.*;
class ChageChar
{
    public static void main(String[] args)
    {
        String str;
        int i;
        char[] array = new char [100];
        Scanner in = new Scanner(System.in);
        str = in.nextLine();
        for (i=0; i<100;i++ )
        {
            array[i] = str.charAt(i);
            System.out.println(array[i]);
        }
        
    }
}
以这个为例子

谢谢各位忠告