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

/**
 * 駝峰命名轉換
 * 
 * @author 47475
 *
 */
public class Tool {
	private static Pattern linePattern = Pattern.compile("_(\\w)");

	/**
	 * 下劃線轉駝峰 ,大寫自動轉小寫<br />
	 * 例如：USER_NAME->userName<br />
	 * USERNAME->userName<br />
	 * USER_NAME->userName<br />
	 * fParentNoLeader->fParentNoLeader
	 * 
	 */
	public static String lineToHump(String str) {
		/** 正則表示式寫法 */
		str = str.toLowerCase();
		Matcher matcher = linePattern.matcher(str);
		StringBuffer sb = new StringBuffer();
		while (matcher.find()) {
			matcher.appendReplacement(sb, matcher.group(1).toUpperCase());
		}
		matcher.appendTail(sb);
		return sb.toString();
		/** 字串比較寫法 */
		/*
		 * if (str == null || "".equals(str.trim())) { return ""; } int len =
		 * str.length(); StringBuilder sb = new StringBuilder(len); for (int i = 0; i <
		 * len; i++) { char c = str.charAt(i); if (c == '_') { if (++i < len) {
		 * sb.append(Character.toUpperCase(str.charAt(i))); } } else { sb.append(c); } }
		 * return sb.toString();
		 */
	}

	private static Pattern humpPattern = Pattern.compile("[A-Z]");

	/**
	 * 駝峰轉下劃線,大寫自動轉小寫<br />
	 * 例如： USER_NAME->user_name USERNAME->userName<br />
	 * f_parent_no_leader->f_parent_no_leader
	 */
	public static String humpToLine(String str) {
		/** 簡單寫法，效率不高 */
//		return str.replaceAll("[A-Z]", "_$0").toLowerCase();
		/** 正則表示式高效寫法 */
		Matcher matcher = humpPattern.matcher(str);
		StringBuffer sb = new StringBuffer();
		while (matcher.find()) {
			matcher.appendReplacement(sb, "_" + matcher.group(0).toLowerCase());
		}
		matcher.appendTail(sb);
		return sb.toString();
		/** 字串比較寫法 */
		/*
		 * if (str == null || "".equals(str.trim())) { return ""; } int len =
		 * str.length(); StringBuilder sb = new StringBuilder(len); for (int i = 0; i <
		 * len; i++) { char c = str.charAt(i); if (Character.isUpperCase(c)) {
		 * sb.append('_'); sb.append(Character.toLowerCase(c)); } else { sb.append(c); }
		 * } return sb.toString();
		 */
	}

	public static void main(String[] args) {
		System.out.println(lineToHump("user_name"));// userName
		System.out.println(humpToLine("userName"));// user_name
	}
}