方法1:
String res = UUID.randomUUID().toString();
res = res.substring(0, 5);
System.out.println(res);
方法2:
String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
str=str.toLowerCase();
str += "1234567890";
StringBuilder sb = new StringBuilder(5);
for(int i = 0; i < 5; i++){
//角标[0,62)
int index = new Random().nextInt(str.length());
char ch = str.charAt(index);
sb.append(ch);
}
System.out.println(sb);