MyRandom.java

package common;

import java.util.Random;

public class MyRandom {
    private String alphabets = "abcdefghijklmnopqrstuvwxyz";
    private String numbers = "0123456789";
    private String alphanumerics = numbers + alphabets;

    public String randomizer(String validChars, int length){
        Random random = new Random();
        char[] charArray = validChars.toCharArray();
        String output = "";
        for(int a=0; a<length; a++){
            output += charArray[random.nextInt(charArray.length)];
        }
        return output;
    }

    public String randomAlphabets(int length){
        return randomizer(alphabets,length);
    }

    public String randomNumbers(int length){
        return randomizer(numbers, length);
    }

    public String randomAlphanumerics(int length){
        return randomizer(alphanumerics, length);
    }

    public String randomBin(){
        return randomizer("123456789",1)+randomNumbers(5);
    }

    public String randomLuhn(String bin){
        int remainder = 15 - bin.length();
        String fifteen = bin + randomNumbers(remainder);
        return fifteen + getChecksum(fifteen);
    }

    private String getChecksum(String fifteen){
        int total = 0;
        for(int a=0; a<fifteen.length(); a++){
            total += getDigit(fifteen, a);
        }
        int remainder = total % 10;
        int output = 0;
        if(remainder > 0){
            output = 10 - remainder;
        }
        return output+"";
    }

    private int getDigit(String fifteen, int index){
        char[] charArray = fifteen.toCharArray();
        int output = 0;
        if(index%2 == 0){
            output = Integer.parseInt(charArray[index]+"") *2;
        } else {
            output = Integer.parseInt(charArray[index]+"");
        }
        if(output>9){
            char[] temp = (output+"").toCharArray();
            output = Integer.parseInt(temp[0]+"")+Integer.parseInt(temp[1]+"");
        }
        return output;
    }
}