Java生成随机数

public class NumUtil {
	
	/**
	 *  随机数生成器
	 *  @param digit 位数      
	 *  @return
	 */
	public static String randomGenerator(int digit){
		int[] nums = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
		
		Random rand = new Random();
		for (int i = 10; i > 1; i--) {
			int index = rand.nextInt(i);
			int tmp = nums[index];
			nums[index] = nums[i - 1];
			nums[i - 1] = tmp;
		}
		
		int result = 0;
		for(int i = 0; i < digit; i++){
			result = result * 10 + nums[i];
		}
		
		String digitString = Integer.toString(result);
		if (digitString.length() == digit-1) {
			digitString = "0" + digitString;
		}
		
		return digitString;
	}
}