I have sample xml content set in a string like,

String s = "<MainInfo><Info><Param1>123</Param1><Param2>santhosh</Param2><Param3>001</Param3></Info><Info><Param1>123</Param1><Param2>santhosh</Param2><Param3>001</Param3>";

Now,I want to validate this ,If the xml content is valid with respect to opening and closing tags,the entered content does not have invalid junk tags etc....some validations like this.
If(valid)
{
say success;
}
else
{
say fail;
}

There are tools that exist to do this already. Is there any reason to not use them?