在Java中验证IPv4字符串 [英] Validating IPv4 string in Java

问题描述

Bellow方法验证字符串是否正确IPv4地址如果有效则返回true。任何正则表达式和优雅的改进都将非常受欢迎：

Bellow method is validating if string is correct IPv4 address it returns true if it is valid. Any improvements in regex and elegance would be very appreciated:

public static boolean validIP(String ip) {
    if (ip == null || ip.isEmpty()) return false;
    ip = ip.trim();
    if ((ip.length() < 6) & (ip.length() > 15)) return false;

    try {
        Pattern pattern = Pattern.compile("^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$");
        Matcher matcher = pattern.matcher(ip);
        return matcher.matches();
    } catch (PatternSyntaxException ex) {
        return false;
    }
}

推荐答案

这里是一种更容易阅读，效率稍低的方式。

Here is an easier-to-read, slightly less efficient, way you could go about it.

public static boolean validIP (String ip) {
    try {
        if ( ip == null || ip.isEmpty() ) {
            return false;
        }

        String[] parts = ip.split( "\\." );
        if ( parts.length != 4 ) {
            return false;
        }

        for ( String s : parts ) {
            int i = Integer.parseInt( s );
            if ( (i < 0) || (i > 255) ) {
                return false;
            }
        }
        if ( ip.endsWith(".") ) {
            return false;
        }

        return true;
    } catch (NumberFormatException nfe) {
        return false;
    }
}

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