java如何随机生成定长的字符串

小数，字符串、时间等示例代码

public class RandomTest {

    public static Random rand = new Random(); public static String dateStart = "2017-01-01 00:00:00"; /** * hh 表示12小时制 * HH 表示24小时制 */ public static SimpleDateFormat format = new SimpleDateFormat("YYYY-MM-DD HH:mm:ss"); public static SimpleDateFormat format1 = new SimpleDateFormat("YYYYMMDDHHmmss"); public static void main(String[] args) throws ParseException { System.out.println(getDouble()); long timeStart = 1483200000000l; System.out.println(format.parse(dateStart).getTime()); System.out.println(format.format(new Date(timeStart))); System.out.println(format.format(new Date(timeStart+1000))); System.out.println(format.format(new Date(timeStart+2000))); format.format(new Date()); System.out.println(getRandomString(2)); } /** * 随机生成指定精确度的小数 * @return */ public static double getDouble(){ DecimalFormat df=new DecimalFormat("#.000000"); int a=(int)(Math.random()*2+1); int aa=(int)(Math.pow(-1, a)); return Double.valueOf(df.format(rand.nextDouble()*100*aa)); } /** * 生成固长字符串 * @param length * @return */ public static String getRandomString(int length) { //length表示生成字符串的长度 String base = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; Random random = new Random(); StringBuffer sb = new StringBuffer(); for (int i = 0; i < length; i++) { int number = random.nextInt(base.length()); sb.append(base.charAt(number)); } return sb.toString(); } /** * 生成固长字符串 * @param length * @return */ public static String getRandomStringNum(int length) { //length表示生成字符串的长度 String base = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; Random random = new Random(); StringBuffer sb = new StringBuffer(); for (int i = 0; i < length; i++) { int number = random.nextInt(base.length()); sb.append(base.charAt(number)); } return sb.toString(); } }

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