maven:

<dependency>
	<groupId>cn.hutool</groupId>
	<artifactId>hutool-all</artifactId>
	<version>4.0.0</version>
</dependency>

java:

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Date;
import java.util.Enumeration;
import java.util.Random;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import cn.hutool.core.date.DateUtil;

/**
 * 字串工具類
 */
public class StringUtil {

	public static String IP = getIp();
	
	/**
	 * 驗證字串是否為數字
	 */
	public static boolean isNumeric(String str) {
		Pattern pattern = Pattern.compile("[0-9]*");
		Matcher isNum = pattern.matcher(str);
		if (!isNum.matches()) {
			return false;
		}
		return true;
	}
	
	/**
	 * 驗證是否為空
	 */
	public static String checkIsNull(String name, Object value) throws NullPointerException {
		if (value == null || "".equals(value)) {
			throw new NullPointerException("欄位[" + name + "]不能為空.");
		}
		return String.valueOf(value);
	}

	// 判斷是否為NULL,如果為NULL則返回""
	public static String strFormatNull(Object object) {
		if (object == null) {
			return "";
		}
		// 如果object為null, String.toString()會報錯. String.valueOf()返回字串NULL
		return String.valueOf(object);
	}
	
	// 判斷是否為NULL,如果為NULL則返回""
	public static int strFormatInt(Object object) {
		if (object == null || "".equals(object)) {
				return 0;
		}
		return Integer.valueOf(object.toString());
	}
	
	// 判斷是否為NULL,如果為NULL則返回""
	public static double strFormatDouble(Object object) {
		if (object == null || "".equals(object)) {
				return 0;
		}
		return Double.valueOf(object.toString());
	}
	
	// 對double保留兩位小數
	public static double formatDouble2(double d) {
        BigDecimal bg = new BigDecimal(d).setScale(2, RoundingMode.UP);
        return bg.doubleValue();
    }
	
	public static String getOrderNo(){
		return DateUtil.format(new Date(), "yyyyMMddHHmmss") + getRandomNum(6);
	}
	
	/**
	 * 獲取隨機數
	 */
	private static final String RANDOM_BASE = "0123456789";
	public static String getRandomNum(int length){
		int randomNum;
        char randomChar;
        Random random = new Random();
        StringBuffer str = new StringBuffer();
        for (int i = 0; i < length; i++) {
            randomNum = random.nextInt(RANDOM_BASE.length());
            randomChar = RANDOM_BASE.charAt(randomNum);
            str.append(randomChar);
        }
        return str.toString();
	}
	
	/**
	 * 獲取隨機字串
	 */
	private static final String BASE = "abcdefghijklmnopqrstuvwxyz0123456789";
	public static String getRandomStr(int length) {
        int randomNum;
        char randomChar;
        Random random = new Random();
        StringBuffer str = new StringBuffer();
        for (int i = 0; i < length; i++) {
            randomNum = random.nextInt(BASE.length());
            randomChar = BASE.charAt(randomNum);
            str.append(randomChar);
        }
        return str.toString();
    }
	
	/**
	 * 獲取本機IP: 支援windows&linux
	 */
	@SuppressWarnings("rawtypes")
	private static String getIp() {
		Enumeration allNetInterfaces;
		try {
			allNetInterfaces = NetworkInterface.getNetworkInterfaces();
			InetAddress ip = null;
			while (allNetInterfaces.hasMoreElements()) {
				NetworkInterface netInterface = (NetworkInterface) allNetInterfaces.nextElement();
				Enumeration addresses = netInterface.getInetAddresses();
				while (addresses.hasMoreElements()) {
					ip = (InetAddress) addresses.nextElement();
					if (ip != null && ip instanceof Inet4Address) {
						if (!"127.0.0.1".equals(ip.getHostAddress())) {
							return ip.getHostAddress();
						}
					}
				}
			}
		} catch (SocketException e) {
		}
		return "127.0.0.1";
	}
	
	public static String getAddress() {
		return IP;
	}
	
}