RandomUtils随机工具类

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public class RandomUtils {
	// 制定字符串范围的因子
	public static final String NUMBERS_AND_LETTERS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
	public static final String NUMBERS = "0123456789";
	public static final String LETTERS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
	public static final String CAPITAL_LETTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
	public static final String LOWER_CASE_LETTERS = "abcdefghijklmnopqrstuvwxyz";
	// 获取随机数字、字母字符串
	public static String getRandomNumbersAndLetters(int length) {
		return getRandom(NUMBERS_AND_LETTERS, length);
	}
	// 获取随机数字字符串
	public static String getRandomNumbers(int length) {
		return getRandom(NUMBERS, length);
	}
	// 获取英文字母组成的随机字符串
	public static String getRandomLetters(int length) {
		return getRandom(LETTERS, length);
	}
	// 获取大写字母组成的随机字符串
	public static String getRandomCapitalLetters(int length) {
		return getRandom(CAPITAL_LETTERS, length);
	}
	// 获取小写字母组成的随机字符串
	public static String getRandomLowerCaseLetters(int length) {
		return getRandom(LOWER_CASE_LETTERS, length);
	}
	// 获取制定字符串和长度的随机字符串
	public static String getRandom(String source, int length) {
		return TextUtils.isEmpty(source) ? null : getRandom(
				source.toCharArray(), length);
	}
	// 获取制定字符数组和长度的随机字符串
	public static String getRandom(char[] sourceChar, int length) {
		if (sourceChar == null || sourceChar.length == 0 || length < 0) {
			return null;
		}

		StringBuilder str = new StringBuilder(length);
		Random random = new Random();
		for (int i = 0; i < length; i++) {
			str.append(sourceChar[random.nextInt(sourceChar.length)]);
		}
		return str.toString();
	}
	
	// 获取0~max范围的随机int
	public static int getRandom(int max) {
		return getRandom(0, max);
	}
	
	// 获取min~max范围的随机int
	public static int getRandom(int min, int max) {
        if (min > max) {
            return 0;
        }
        if (min == max) {
            return min;
        }
        return min + new Random().nextInt(max - min);
    }

}