java变量有下划线 java将下划线转为驼峰

java转换下划线为驼峰的2中方式

public static void main(String[] args) {
        System.out.println(patternHump("sys_user_id"));
        System.out.println(hump("sys_user_id"));
    }
    
	public static String hump(String str) {
        char[] chars = str.toCharArray();
        for (int i = 0; i < chars.length; i++) {
            if (chars[i] == '_') {
                if (i == chars.length - 1) {
                    break;
                }
                if (chars[i + 1] >= 97 && chars[i+1] <= 122) {
                    int upper = chars[i + 1] - (2 << 4);
                    chars[i + 1] = (char) upper;
                }
            }
        }
        return new String(chars).replace("_","");
    }
    
    static Pattern pattern = Pattern.compile("_(.)");
    public static String patternHump(String str) {
        StringBuffer sb = new StringBuffer();
        Matcher matcher = pattern.matcher(str);
        while (matcher.find()) {
            String group = matcher.group(1);
            matcher.appendReplacement(sb, group.toUpperCase());
        }
        matcher.appendTail(sb);
        return sb.toString();
    }