Random Verification Code Generation code

Random Verification Code Generation code
     PackageCom.zuidaima.core.util; ImportJava.util.Random;  Public classRandomutil { Public Static FinalString Allchar = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";  Public Static FinalString Letterchar = "ABCDEFGHIJKLLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ";  Public Static FinalString Numberchar = "0123456789"; /*** Returns a fixed-length random string (containing only uppercase and lowercase letters, numbers) * *@paramlength * Random string lengths *@returnRandom String*/           Public StaticString generatestring (intlength) {StringBuffer SB=NewStringBuffer (); Random Random=NewRandom ();  for(inti = 0; i < length; i++) {sb.append (Allchar.charat (Random.nextint (Allchar.length ()))); }              returnsb.tostring (); }                /*** Returns a fixed-length random plain letter string (with uppercase and lowercase letters only) * *@paramlength * Random string lengths *@returnRandom String*/           Public StaticString generatemixstring (intlength) {StringBuffer SB=NewStringBuffer (); Random Random=NewRandom ();  for(inti = 0; i < length; i++) {sb.append (Allchar.charat (Random.nextint (Letterchar.length ()))); }              returnsb.tostring (); }                /*** Returns a fixed-length random pure capital letter string (with uppercase and lowercase letters only) * *@paramlength * Random string lengths *@returnRandom String*/           Public StaticString generatelowerstring (intlength) {              returngeneratemixstring (length). toLowerCase (); }                /*** Returns a fixed-length random plain lowercase letter string (with only uppercase letters) * *@paramlength * Random string lengths *@returnRandom String*/           Public StaticString generateupperstring (intlength) {              returngeneratemixstring (length). toUpperCase (); }                /*** Generate a fixed-length pure 0 String * *@paramLength * String lengths *@returnPure 0 String*/           Public StaticString generatezerostring (intlength) {StringBuffer SB=NewStringBuffer ();  for(inti = 0; i < length; i++) {sb.append (' 0 '); }              returnsb.tostring (); }                /*** Generate a fixed-length string based on the number, the length is not enough for the front 0 * *@paramnum * Number *@paramFixdlenth * String length *@returnfixed-length string*/           Public StaticString tofixdlengthstring (LongNumintfixdlenth) {StringBuffer SB=NewStringBuffer (); String Strnum=string.valueof (num); if(Fixdlenth-strnum.length () >= 0) {sb.append (generatezerostring (Fixdlenth-strnum.length ())); } Else {                  Throw NewRuntimeException ("Convert number + num +" to length "+Fixdlenth+ "The string has an exception! ");              } sb.append (Strnum); returnsb.tostring (); }                /*** The number of Len bits generated each time is different * *@paramparam *@returnfixed-length numbers*/           Public Static intGetnotsimple (int[] param,intLen) {Random Rand=NewRandom ();  for(inti = param.length; i > 1; i--) {                  intindex =Rand.nextint (i); intTMP =Param[index]; Param[index]= Param[i-1]; Param[i-1] =tmp; }              intresult = 0;  for(inti = 0; i < Len; i++) {result= result * 10 +Param[i]; }              returnresult; }                 Public Static voidMain (string[] args) {System.out.println ("Returns a fixed-length random string (containing only uppercase and lowercase letters, numbers):" + generatestring (10)); System.out. println ("Returns a fixed-length random, pure-letter string (with uppercase and lowercase letters only):" + generatemixstring (10)); System.out.println ("Returns a fixed-length random, purely uppercase string (with uppercase and lowercase letters only):" + generatelowerstring (10)); System.out.println ("Returns a fixed-length random plain lowercase letter string (with only uppercase letters):" + generateupperstring (10)); System.out.println ("Generate a fixed-length pure 0 string:" + generatezerostring (10)); System.out.println ("Generates a fixed-length string based on a number that is not longer than the previous 0:" + tofixdlengthstring (123, 10)); int[] in = {1, 2, 3, 4, 5, 6, 7 }; System.out.println ("The number of Len bits generated each time is different:" + getnotsimple (in, 3)); }      }  

Random Captcha Code generation (RPM)