/**
 * 工具类-驼峰和下划线的转换
 */
public class StringUtil {


    /**
     * 下划线命名转驼峰命名
     * @param underscore
     * @return
     */
    public static String underscoreToCamelCase(String underscore){
        String[] ss = underscore.split("_");
        if(ss.length ==1){
            return underscore;
        }

        StringBuffer sb = new StringBuffer();
        sb.append(ss[0]);
        for (int i = 1; i < ss.length; i++) {
            sb.append(upperFirstCase(ss[i]));
        }

        return sb.toString();
    }

    /**
     * 驼峰 转下划线
     * @param camelCase
     * @return
     */
    public static String toLine(String camelCase){
        Pattern humpPattern = Pattern.compile("[A-Z]");
        Matcher matcher = humpPattern.matcher(camelCase);
        StringBuffer sb = new StringBuffer();
        while(matcher.find()){
            matcher.appendReplacement(sb, "_"+matcher.group(0).toLowerCase());
        }
        matcher.appendTail(sb);
        return sb.toString();
    }


    /**
     * 首字母 转小写
     * @param str
     * @return
     */
    private static String lowerFirstCase(String str) {
        char[] chars = str.toCharArray();
        chars[0] += 32;
        return String.valueOf(chars);
    }

    /**
     * 首字母 转大写
     * @param str
     * @return
     */
    private static String upperFirstCase(String str) {
        char[] chars = str.toCharArray();
        chars[0] -= 32;
        return String.valueOf(chars);
    }


    public static void main(String[] args) {
        String camelCase = StringUtil.underscoreToCamelCase("cteate_time");
        System.out.println(camelCase);//cteateTime

        System.out.println(toLine("cteateTimeAndUser"));//cteate_time_and_user
    }
}