随机产生字母a--z, A-Z 的任意组合

VERSION 1.0 引自： http://www.coderanch.com/t/134491/Security/generating-secure-tokens

package demo;

import java.util.Random;

/*

* This code is a discussion of an opinion in a technical forum.

* You may develope ideas from this code. You may not use it directly.

*/

public class DM

{

String getRandomIdentifier(int length) throws Exception

{

final int limitingValue = 64;// Whatever you decide, not me.

if(length < limitingValue)

{

try

{

// The first step is to get a filename generator

char lowerBound = 'a';

char upperBound = 'z';

Random randomCharacterGenerator = new Random();

// Then get some characters

char[] identifierBuffer = new char[length];//

int index = identifierBuffer.length;//

final int numericLowerBound = (int) lowerBound;

final int numericUpperBound = (int) upperBound;

final int range = numericUpperBound - numericLowerBound;//

do

{

// recoded in mesage edit, original defective

int getOne = randomCharacterGenerator.nextInt(range);

int next = numericLowerBound + getOne;

identifierBuffer[--index] = (char) next;

}

while(index > 0x00000000);

return new String(identifierBuffer);//

}

catch(ArrayIndexOutOfBoundsException aioobe)

{

System.out.println(aioobe.getMessage());

}

else

{

throw new Exception("Contact system administrator.");//

}

return null;

}

VERSION 2.0 改进型：

package token;

import java.util.Random;

public class DM {
   public static void main(String[] args) throws Exception {
       System.out.println("1==97===:" + (int) 'a');
       System.out.println("2==122===:" + (int) 'z');
       System.out.println("3==65===:" + (int) 'A');
       System.out.println("4===90==:" + (int) 'Z');
       DM mn = new DM();
       System.out.println(mn.getRandomIdentifier(26));
   }

String getRandomIdentifier(int length) throws Exception {
       final int limitingValue = 164;// Whatever you decide, not me.
       if (length < limitingValue) {
           try {
               // 26个小写+26个大小 = 52 字母
               final int range = 52;//
               char[] charStr = new char[range];
               int j = 0;
               // A=65, z =122
               for (int i = 65; i <= 122; i++) {
                   // Z--a 之间的跳过
                   if (i > 90 && i < 97) {
                       continue;
                   }
                   charStr[j] = (char) i;   // 这里将保存52个大小字母
                   j++;
               }

// 这里其实可以将 0 - 9 的数字也添加进去
               Random randomCharacterGenerator = new Random();
               // Then get some characters
               char[] identifierBuffer = new char[length];//
               int index = identifierBuffer.length;//
               do {
                   // 产生0至51 共52个随机数，用于索引字母数组
                   int getOne = randomCharacterGenerator.nextInt(range);
                   identifierBuffer[--index] = charStr[getOne];
               } while (index > 0x00000000);
               return new String(identifierBuffer);//
           } catch (ArrayIndexOutOfBoundsException aioobe) {
               System.out.println(aioobe.getMessage());
           }
       } else {
           throw new Exception("Contact system administrator.");//
       }
       return null;
   }

}

巴特西

随机产生字母a--z, A-Z 的任意组合

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