Commonly used Java regular expressions

1. Java method to determine whether a string is an integer or a decimal:

matches() method: used to detect whether a string matches a given regular expression.
EX: str.matches("regular expression")
regular expression:

//判断是否是整数或4位内的小数
[+-]?[0-9]+(\\.[0-9]{
    
    1,4})?
//判断是否是整数或不限制小数位的小数
[+-]?[0-9]+(\\.[0-9]+)?

2. Mobile phone number legality verification

Verification of mainland mobile phone number:

package com.utils;
 
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
 
/**
 * 手机号校验工具类
 *
 * @author Duncino
 * @date 2021/12/23
 */
public class PhoneCheckUtils {
    
    
 
    /**
     * 大陆手机号码11位数，匹配格式：前三位固定格式+后8位任意数
     */
    public static boolean isPhoneLegal(String phone) throws PatternSyntaxException {
    
    
        String regex = "^((13[0-9])|(14[05679])|(15([0-3,5-9]))|(16[2567])|(17[01235678])|(18[0-9]|19[135689]))\\d{8}$";
        Pattern p = Pattern.compile(regex);
        Matcher m = p.matcher(phone);
        boolean isMatch = m.matches();
        return isMatch;
    }
}

3. Email regular expression

Email verification rules:

1. There must be content before @ and it can only be letters (uppercase and lowercase), numbers, underscores (_), minus signs (-), and dots (.)
2. There must be content between @ and the last dot (.) and it can only be letters (upper and lower case), numbers, dots (.), and minus signs (-), and the two dots cannot be next to each other.
3. There must be content after the last dot (.) and the content can only be letters (upper and lower case), numbers, and the length is greater than or equal to 2 bytes and less than or equal to 6 bytes.

Regular expression for email verification:

^[a-zA-Z0-9_.-]+@[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)*\.[a-zA-Z0-9]{
    
    2,6}$