求txt内数字之和，除了数字之外，别的字符之类的东西不会转化位数字-Seeking the txt Figures and outside, in addition to digital, the other characters like something not translate digit

字符表示的十六进制数转化为相应的整数    错误则返回    -1   -said the character hexadecimal number into the corresponding integer

1.写一个处理字符串的类，包含以下类方法：将字符串里大写字符变小写，小写字符变大写；在字符串中寻找子串的个数和分别出现的位置；将字符串转化为数字，并自动忽略非数字字符；找出两个字符串中相同字符的个数.-1. Write a string handling class that contains the following class method: a string in uppercase characters to lowercase, uppercase becomes lowercase