java一些工具类

import java.math.BigDecimal;

import java.math.RoundingMode;

import java.util.ArrayList;

import java.util.List;

import java.util.Random;

import java.util.regex.MatchResult;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

/**

 * @author: tomingto

 *

 **/

public class NumberUtils {

    public static boolean isInt(Double num) {

        return num.intValue() == num;

    }

    /**

     * 判断字符串是否是数值格式

     * @param str

     * @return

     */

    public static boolean isDigit(String str){

        if(str == null || str.trim().equals("")){

            return false;

        }

        return str.matches("^\\d+$");

    }

    /**

     * 将一个小数精确到指定位数

     * @param num

     * @param scale

     * @return

     */

    public static double scale(double num, int scale) {

        BigDecimal bd = new BigDecimal(num);

        return bd.setScale(scale, RoundingMode.HALF_UP).doubleValue();

    }

    // 从字符串中根据正则表达式寻找，返回找到的数字数组

    public static Double[] searchNumber(String value, String regex){

        List<Double> doubles = new ArrayList<>();

        Pattern pattern = Pattern.compile(regex);

        Matcher matcher = pattern.matcher(value);

        if(matcher.find()) {

            MatchResult result = matcher.toMatchResult();

            for (int i = 1; i <= result.groupCount(); i++) {

                doubles.add(Double.valueOf(result.group(i)));

            }

        }

        return doubles.toArray(new Double[doubles.size()]);

    }

    /**

     * 生成指定位数的随机数字

     * @param len

     * @return

     */

    public static String generateCode(int len){

        len = Math.min(len, 8);

        int min = Double.valueOf(Math.pow(10, len - 1)).intValue();

        int num = new Random().nextInt(Double.valueOf(Math.pow(10, len + 1)).intValue() - 1) + min;

        return String.valueOf(num).substring(0,len);

    }

}