pwdgen

import java.util.Random;

public class PwdGen {

	private static final char[] SPECIAL_CHAR_TABLE = { '(', ')', '-', '_', '=',
			'[', ']', '{', '}', ':', ',', '.', '?', '!', '*', '$', '#', '%' };
	private static final Random rnd = new Random();

	/**
	 * 按指定长度和级别生成密码
	 * 
	 * @param Len
	 *            密码长度,最少4位
	 * @param level
	 *            密码级别 0.数字 ; 1.字母; 2.数字+字母 ;3.数字+字母＋特殊字符
	 * @return
	 */
	public static String buildPwd(int Len, int level) {

		if (Len < 4) {
			Len = 4;
		}
		String temprandomPwd = "";
		String randomPwd = "";
		String finalpwd = "";
		int ir = rnd.nextInt(Len);

		switch (level) {
		case 0:// 数字

			for (int i = 0; i < Len; i++) {
				temprandomPwd += rnd.nextInt(10);
			}
			finalpwd = changeLocation(temprandomPwd);
			break;
		case 1:// 字母
			for (int i = 0; i < Len; i++) {
				temprandomPwd += genLetter(1, 0) + genLetter(1, 1);
			}
			randomPwd = temprandomPwd.substring(ir, Len + ir);
			finalpwd = changeLocation(randomPwd);
			break;
		case 2:// 数字＋字母
			for (int i = 0; i < Len; i++) {
				temprandomPwd += rnd.nextInt(10) + genLetter(1, 0)
						+ genLetter(1, 1);
			}
			randomPwd = temprandomPwd.substring(Len + ir, Len * 2 + ir);
			finalpwd = changeLocation(randomPwd);
			break;
		default:// 数字＋字母+特殊符号
			for (int i = 0; i < Len; i++) {

				temprandomPwd += rnd.nextInt(10) + genSpecialChar(1)
						+ genLetter(1, 0) + genLetter(1, 1);
			}
			randomPwd = temprandomPwd.substring(Len + ir, Len * 2 + ir);
			finalpwd = changeLocation(randomPwd);
			break;
		}
		return finalpwd;
	}

	public static String genLetter(final int num, final int flag) {
		char[] arr = new char[num];
		char baseChar = flag == 0 ? 'A' : 'a';
		for (int i = 0; i < num; i++) {
			arr[i] = (char) (baseChar + rnd.nextInt(26));
		}
		return new String(arr);
	}

	public static String genSpecialChar(final int num) {
		char[] arr = new char[num];
		for (int i = 0; i < num; i++) {
			arr[i] = SPECIAL_CHAR_TABLE[rnd.nextInt(SPECIAL_CHAR_TABLE.length)];
		}
		return new String(arr);
	}

	public static String changeLocation(final String value) {
		char[] arr = value.toCharArray();

		for (int i = arr.length; i > 1; i--) {
			swap(arr, i - 1, rnd.nextInt(i));
		}

		return new String(arr);
	}
	private static void swap(final char[] arr, final int i, final int j) {
		char tmp = arr[i];
		arr[i] = arr[j];
		arr[j] = tmp;
	}
}