转小驼峰

//下划线对小驼峰命名转换
public class UnderlineToCamelCase {
    public static String underlineToCamel(String underlineStr) {
        String[] words = underlineStr.split("_");
        StringBuilder result = new StringBuilder(words[0]);
        // 从第二个单词开始，将每个单词的首字母大写，并添加到结果中
        for (int i = 1; i < words.length; i++) {
            String word = words[i];
            if (word.length() > 0) {
                result.append(Character.toUpperCase(word.charAt(0)));
                if (word.length() > 1) {
                    result.append(word.substring(1));
                }
            }
        }
        return result.toString();
    }

    public static void main(String[] args) {
        System.out.println(underlineToCamel("user_name")); 
    }
}

转大驼峰

public class UnderlineToBigCamelCase {
    public static String underlineToBigCamel(String underlineStr) {
        StringBuilder result = new StringBuilder();
        String[] words = underlineStr.split("_");
        // 遍历每个单词
        for (String word : words) {
            if (word.length() > 0) {
                result.append(Character.toUpperCase(word.charAt(0)));
                if (word.length() > 1) {
                    result.append(word.substring(1));
                }
            }
        }
        return result.toString();
    }

    public static void main(String[] args) {
        System.out.println(underlineToBigCamel("user_name")); 
    }
}