随机数

方法一：

/**
     * 获取16位以内的随机数字符串
     * @return
     */
    public static String getNonceStr(int num){
    	// Math.random()的结果是个double类型的值，区间为[0.0,1.0）
    	if(num>0&&num<=16){
    		String str=String.valueOf(Math.random()).substring(2);//16位随机数
            return str.substring(0,num);
    	}
        return "";
    }

方法二：

import java.util.Random;

public class StringDemo {
	public static void main(String[] args) {
		String temp=generateRandomString();
		System.out.println("长度8位的随机字符串="+temp);
	}
	
    /**
     * 随机生成字符串
     * 
     * @return
     */
    private static String generateRandomString() {
    	final int FIXED=8;//生成的随机字符串长度
        final String originStr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
        final Random random = new Random();
        final StringBuffer buffer = new StringBuffer();
        for (int i = 0; i < FIXED; i++) {
            final Character ch = originStr.charAt(random.nextInt(originStr.length()));
            buffer.append(ch);
        }
        return buffer.toString();
    }
}