Question

java 实现生成随机的四位代码，字母或者数字，字母区分大小写

Answer 1

String getRandom() {
Random rand = new Random(new Date().getTime());
int cnt = 26 * 2 + 10;
char[] s = new char[4];
for (int i = 0; i < 4; i++) {
int v = rand.nextInt(cnt);
if (v < 10)
s[i] = '0' + v;
else if (v < 36)
s[i] = v - 10 + 'A';
else
s[i] = v - 36 + 'a';
}
return new String(s);
}