How to get the Username only the characters not the whitespaces?

In jsp applic开发者_运维技巧ation, i am checking username and password, when entering whitespace in username means it didnt show the error, how to validate it?

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Maybe you want to trim() the value before checking the username/password:

String password = getPassword().trim();

This will remove all leading and trailing whitespaces.

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Why do you do it in the back end, you can use a javascrit regex :

^([a-zA-Z0-9.]+@){0,1}([a-zA-Z0-9.])+$

This will permit A-Z, a-z, 0-9 and ., and at most one @

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Do a regex validation, if your username contains only digits and alphabets, do something like

[A-Za-z0-9]+

Change it based on length limitations

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You have two different questions:

1. How to get the Username only the characters not the whitespaces?

   To do that, you can simply replace all the whitespaces in your string:

   String name = " blah is a word";
   name = name.replace(" ", "");
   

2. How to validate the username?

   To do that, you can simply check if the string contains a whitespace.

   String name = " blah is a word";
   if (name.contains(" "))
   {
       // Wrong
   } else
   {
       // Correct
   }