Java之驼峰和下划线命名的相互转化-yellowcong

在数据库命名为下划线大写的方式，我们需要通过驼峰命名转化工具，将名称转化为驼峰，然后生成java的entity,在这个工具包中，通过正则表达式的方式，进行匹配，然后进行命名转化

工具包

package com.yellowcong.utils;

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

public class StringUtils {

    /**
     * 下划线转驼峰法(默认小驼峰)
     *
     * @param line
     *            源字符串
     * @param smallCamel
     *            大小驼峰,是否为小驼峰(驼峰，第一个字符是大写还是小写)
     * @return 转换后的字符串
     */
    public static String underline2Camel(String line, boolean ... smallCamel) {
        if (line == null || "".equals(line)) {
            return "";
        }
        StringBuffer sb = new StringBuffer();
        Pattern pattern = Pattern.compile("([A-Za-z\\d]+)(_)?");
        Matcher matcher = pattern.matcher(line);
        //匹配正则表达式
        while (matcher.find()) {
            String word = matcher.group();
            //当是true 或则是空的情况
            if((smallCamel.length ==0 || smallCamel[0] ) && matcher.start()==0){
                sb.append(Character.toLowerCase(word.charAt(0)));
            }else{
                sb.append(Character.toUpperCase(word.charAt(0)));
            }

            int index = word.lastIndexOf('_');
            if (index > 0) {
                sb.append(word.substring(1, index).toLowerCase());
            } else {
                sb.append(word.substring(1).toLowerCase());
            }
        }
        return sb.toString();
    }

    /**
     * 驼峰法转下划线
     *
     * @param line
     *            源字符串
     * @return 转换后的字符串
     */
    public static String camel2Underline(String line) {
        if (line == null || "".equals(line)) {
            return "";
        }
        line = String.valueOf(line.charAt(0)).toUpperCase()
                .concat(line.substring(1));
        StringBuffer sb = new StringBuffer();
        Pattern pattern = Pattern.compile("[A-Z]([a-z\\d]+)?");
        Matcher matcher = pattern.matcher(line);
        while (matcher.find()) {
            String word = matcher.group();
            sb.append(word.toUpperCase());
            sb.append(matcher.end() == line.length() ? "" : "_");
        }
        return sb.toString();
    }

    public static void main(String[] args) {
        String line = "are_you_dou_bi_yellowcong";
        //下划线转驼峰（大驼峰）
        //AreYouDouBiYellowcong
        String camel = underline2Camel(line, false);
        System.out.println(camel);

        //下划线转驼峰（小驼峰）
        //areYouDouBiYellowcong
        camel = underline2Camel(line);
        System.out.println(camel);

        //驼峰转下划线
        //ARE_YOU_DOU_BI_YELLOWCONG
        System.out.println(camel2Underline(camel));
    }
}

测试结果，默认的是小驼峰的方法