JAVA生成隨機文件名

//生成隨機文件名，防止上傳文件后文件名重復
public String generateRandomFilename(){
String RandomFilename = "";
Random rand = new Random();//生成隨機數
int random = rand.nextInt();

Calendar calCurrent = Calendar.getInstance();
int intDay = calCurrent.get(Calendar.DATE);
int intMonth = calCurrent.get(Calendar.MONTH) + 1;
int intYear = calCurrent.get(Calendar.YEAR);
String now = String.valueOf(intYear) + "_" + String.valueOf(intMonth) + "_" +
String.valueOf(intDay) + "_";

RandomFilename = now + String.valueOf(random > 0 ? random : ( -1) * random);

return RandomFilename;
}