Random number Test

Learning Links http://lavasoft.blog.51cto.com/62575/113758/


Import Java.util.Random; /** * Random number, then string tool * User:leizhimin * date:2008-11-19 9:43:09 */public class Randomutils {public static final S         Tring Allchar = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";         public static final String Letterchar = "ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ";         public static final String Numberchar = "0123456789";         /** * Returns a fixed-length random string (containing only uppercase and lowercase letters, numbers) * * @param length random string lengths * @return Random String */                 public static String generatestring (int length) {stringbuffer sb = new StringBuffer ();                 Random random = new random ();                  for (int i = 0; i < length; i++) {Sb.append (Allchar.charat (Random.nextint (Allchar.length ())));         } return sb.tostring (); }/** * Returns a fixed-length random, pure-letter string (containing only uppercase and lowercase letters) * * @param length random string lengths * @returnRandom String */public static string generatemixstring (int length) {stringbuffer sb = new Strin                 Gbuffer ();                 Random random = new random (); for (int i = 0; i < length; i++) {Sb.append (Allchar.charat (Random.nextint (Letterchar.length ())                 ));         } return sb.tostring ();          }/** * Returns a fixed-length random pure capital letter string (with uppercase and lowercase letters only) * * @param length random string lengths * @return Random string */public static String generatelowerstring (int length) {return generatemixstring (length         ). toLowerCase ();          }/** * Returns a fixed-length random plain lowercase letter string (with only uppercase letters) * * @param length random string lengths * @return Random string */public static String generateupperstring (int length) {return generatemixstring (length         ). toUpperCase (); }/** * Generates a fixed-length pure 0 String * * @param length stringLength * @return Pure 0 String */public static string generatezerostring (int length) {Stri                 Ngbuffer sb = new StringBuffer ();                 for (int i = 0; i < length; i++) {sb.append (' 0 ');         } return sb.tostring (); /** * Generates a fixed-length string based on the number, length is not enough for the front 0 * * @param num number * @param fixdlen                 Th string length * @return fixed-length string */public static string tofixdlengthstring (long num, int fixdlenth) {                 StringBuffer sb = new StringBuffer ();                 String strnum = string.valueof (num); if (fixdlenth-strnum.length () >= 0) {sb.append (generatezerostring (Fixdlenth-strnum.length (                 ))); } else {throw new RuntimeException ("Convert number + num +" to a string with a length of "+ Fixdlenth +") An exception occurred!                 ");             } sb.append (Strnum);    return sb.tostring (); /** * Generates a fixed-length string based on the number, length is not enough for the front 0 * * @param num number * @param fixdlen                 Th string length * @return fixed-length string */public static string tofixdlengthstring (int num, int fixdlenth) {                 StringBuffer sb = new StringBuffer ();                 String strnum = string.valueof (num); if (fixdlenth-strnum.length () >= 0) {sb.append (generatezerostring (Fixdlenth-strnum.length (                 ))); } else {throw new RuntimeException ("Convert number + num +" to a string with a length of "+ Fixdlenth +") An exception occurred!                 ");                 } sb.append (Strnum);         return sb.tostring ();                 } public static void Main (string[] args) {System.out.println (generatestring (15));                 System.out.println (generatemixstring (15));                 System.out.println (generatelowerstring (15)); SystEm.out.println (generateupperstring (15));                 System.out.println (generatezerostring (15));                 System.out.println (tofixdlengthstring (123, 15));         System.out.println (Tofixdlengthstring (123L, 15)); } }

Small random number experiment:

Import Java.util.Random; /** * java random number Test * user:leizhimin * date:2008-11-19 17:52:50 * * public class Testrandomnum {public static void M                 Ain (string[] args) {randomtest ();                 Testnoseed ();                 TestSeed1 ();         TestSeed2 ();                 public static void Randomtest () {System.out.println ("--------------test ()--------------");                 Returns the current time in milliseconds.                 Long R1 = System.currenttimemillis ();                 Returns a double value with a positive sign, greater than or equal to 0.0, less than 1.0.                 Double r2 = math.random ();                 By using the random class to get the next random integer int r3 = new Random (). Nextint ();                 System.out.println ("r1 =" + r1);                 SYSTEM.OUT.PRINTLN ("r3 =" + R2);         SYSTEM.OUT.PRINTLN ("r2 =" + R3); public static void Testnoseed () {System.out.println ("--------------testnoseed ()--------------")                 ; To create a test random object without a seed                Random random = new random ();                 for (int i = 0; i < 3; i++) {System.out.println (Random.nextint ()); }} public static void TestSeed1 () {System.out.println ("--------------testSeed1 ()--------                 ------");                 Create a test random object with a seed random random = new Random (555L);                 for (int i = 0; i < 3; i++) {System.out.println (Random.nextint ()); }} public static void TestSeed2 () {System.out.println ("--------------testSeed2 ()--------                 ------");                 Create a test random object with a seed random random = new random ();                 Random.setseed (555L);                 for (int i = 0; i < 3; i++) {System.out.println (Random.nextint ()); }         } }

　　

Random number Test