Java 中使用正则表达式验证用户名

这篇文章主要记录怎样使用java api中的java.util.regex.Matcher 和java.util.regex.Pattern

例如，用户名的正则表达式如下：

^[a-z0-9_-]{3,15}$

上述正则表达式的含义：

^                             # Start of the line
[a-z0-9_-]	     # Match characters and symbols in the list, a-z, 0-9, underscore, hyphen
{3,15}     # Length at least 3 characters and maximum length of 15
$                             # End of the line

完整实例：

package org.hello.reg;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class UsernameValidator {

    private Pattern pattern;
    private Matcher matcher;

    public static void main(String[] args){
        UsernameValidator usernameValidator = new UsernameValidator();
        String[] usernames = new String[6];
        usernames[0] = "hello";
        usernames[1] ="he#llo";
        usernames[2] = "he";
        usernames[3] = "ho_o";
        usernames[4] = "kkkkkkkkkkkkkkkkkkkk";
        usernames[5] = "#####";

        for(String name : usernames){
            boolean valid = usernameValidator.validate(name);
            System.out.println("Username is valid: " + name + " , " + valid);
        }

    }

    private static final String USERNAME_PATTERN = "^[a-z0-9_-]{3,15}$";

    public UsernameValidator(){
        pattern = Pattern.compile(USERNAME_PATTERN);

    }

    public boolean validate(final String username){
        matcher = pattern.matcher(username);
        return matcher.matches();
    }
}

运行结果：

Username is valid: hello , true
Username is valid: he#llo , false
Username is valid: he , false
Username is valid: ho_o , true
Username is valid: kkkkkkkkkkkkkkkkkkkk , false
Username is valid: ##### , false