指定した長さの文字列+チェックをランダムに生成

           ,        app                ,                    ,             .

    ,              :
 1.        ,     ;
 2.        ,     ;
 3.        ,     +     ;

                 .

package com.test;

import java.util.Random;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RandomStringUtil {

    public static void main(String []args){
        System.out.print(randomString(6,6,3));
        System.out.println(matchAccountPattern("Liu123456"));

    }

    private static Object mLock = new Object();
    private static Random random = null;
    private static char[] numbersAndLetters = null;
    public static final int TYPE_UNDEFINE = 0;//undefine
    public static final int TYPE_NUMBER = 1;//numbers only
    public static final int TYPE_LETTER = 2;//letters only
    public static final int TYPE_BOTH = 3;// contains both number and letter
    public static String randomString(int minLength,int maxLength,int type){
         String targetString =null;
        if (minLength < 1) {
            return targetString;
        }
        if (random == null) {
            synchronized (mLock) {
                if (random == null) {
                    random = new Random();
                }
            }
        }

        switch (type) {
            case TYPE_NUMBER:
                numbersAndLetters = ("0123456789").toCharArray();
                break;
            case TYPE_LETTER:
                numbersAndLetters = ("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();
                break;
            case TYPE_UNDEFINE:
            case TYPE_BOTH:
            default:
                numbersAndLetters = ("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();
                break;
        }

        //   65-90 97-122     48-57
        boolean isNumber = false;
        boolean isLetter = false;

        int len = getStringLength(minLength, maxLength, random);
        char[] randBuffer = new char[len];
        for (int i = 0; i < randBuffer.length; i++) {
            randBuffer[i] = numbersAndLetters[random.nextInt(numbersAndLetters.length)];
            if (randBuffer[i] >= 48 && randBuffer[i] <= 57) {
                isNumber = true;
                System.out.println(i+"  randBuffer[i]  "+randBuffer[i]+"  isNumber "+isNumber);
            }
            if ((randBuffer[i] >= 65 && randBuffer[i] <= 90)||(randBuffer[i] >= 97 && randBuffer[i] <= 122)) {
                isLetter = true;
                System.out.println(i+"  randBuffer[i]  "+randBuffer[i]+"  isLetter "+isLetter);
            }
        }
        targetString = new String(randBuffer);
        if (type == TYPE_BOTH) {
            if (!isNumber||!isLetter){
                targetString= randomString(maxLength, minLength, type);
            }
        }
        return targetString;
    }
    /**
     *                        
     *
     * @param minLength     
     * @param maxLength     
     * @param random            
     * @return   
     */
    private static int getStringLength(int minLength, int maxLength, Random random) {
        if (maxLength < minLength) {
            return 0;
        }
        int[] lengthArray = new int[maxLength - minLength + 1];
        for (int a = 0; a <= maxLength - minLength; a++) {
            lengthArray[a] = minLength + a;
        }
        return lengthArray[random.nextInt(lengthArray.length)];
    }

    //     6-16     +    
    public static boolean matchPassWordPattern(String userAccount) {
        String regex = "^(?=.*[0-9])(?=.*[a-zA-Z])([a-zA-Z0-9]{6,16})$";
        Pattern pattern = Pattern.compile(regex);
        Matcher m = pattern.matcher(new String(userAccount));
        return m.matches();
    }
    //8-12 ，  、  ，      、      +    ；  ^[a-z0-9A-Z]{8,12}$
    public static boolean matchAccountPattern(String userAccount) {
        String regex = "^[a-z0-9A-Z]{8,12}$";
        Pattern pattern = Pattern.compile(regex);
        Matcher m = pattern.matcher(new String(userAccount));
        return m.matches();
    }
}