Validation usually is more about just the type of data. Sure, the input is an integer, but maybe it needs to be in the range of 0..10. A string might have to be all lower case. Etc. As the input constraints become more complicated, you are no longer doing just validation, but full-on parsing.
2) There might be lot of numeric data to read. and if we each time type out the validateion for the string,then NO code-reuse. .if we create a validation class,and have validate Int,validate string,will that be correct?wrong?