str1=GetRandomCharString("");;
str3=GetRandomCharString(str1);;
private String GetRandomCharString(String strExclude){
Random randGen = null;
char[] numbersAndLetters = null; if (randGen == null)
{
randGen = new Random();
numbersAndLetters = ("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();
}
char randC;
String randStr="";
randC = numbersAndLetters[randGen.nextInt(61)];
randStr=String.valueOf(randC);
while(strExclude.indexOf(randStr)>0){
randC = numbersAndLetters[randGen.nextInt(61)];
randStr=String.valueOf(randC);
}
return randStr;
}
GetRandomCharString("AB");