Ajuda entendimento de CODIGO GERADOR/VALIDADOR CHAVES

package com.licenses;

import java.util.*;

public class LicenseKey
{

    public String getLicenseKey()
    {
        return licenseKey;
    }

    public void setLicenseKey(String licenseKey)
    {
        this.licenseKey = licenseKey;
    }

    public LicenseKey(LinkedHashMap args)
    {
        this(args, 4);
    }

    public LicenseKey(LinkedHashMap args, int sizeColumns)
    {
        licenseKey = null;
        processLicenseKey(args, sizeColumns);
    }

    private void processLicenseKey(Map args, int sizeColumns)
    {
        StringBuffer buffer = new StringBuffer();
        String keys[] = new String[args.size()];
        String values[] = new String[args.size()];
        byte licKey[] = new byte[args.size() * sizeColumns];
        byte key[] = new byte[sizeColumns];
        Iterator listKeys = args.keySet().iterator();
        for(int i = 0; listKeys.hasNext(); i++)
        {
            keys[i] = (String)listKeys.next();
            values[i] = (String)args.get(keys[i]);
        }

        int pos = 0;
        for(int posi = 0; pos < licKey.length && posi < keys.length;)
        {
            key = truncateValues(keys[posi], values[posi], sizeColumns);
            posi++;
            for(int posx = 0; posx < key.length; posx++)
            {
                licKey[pos] = key[posx];
                pos++;
            }

        }

        for(int x = 0; x < licKey.length; x++)
        {
            licKey[x] = rangeByte(licKey[x]);
            if(x % sizeColumns == 0 && x > 0 && x < licKey.length - 1)
                buffer.append('-');
            buffer.append((char)licKey[x]);
        }

        setLicenseKey(buffer.toString());
    }

    private byte rangeByte(byte bt)
    {
        if(bt < 0)
            bt *= -1;
        if(bt > 0 && bt < 57)
            bt += 57;
        if(bt < 0)
            bt *= -1;
        if(bt > 57 && bt < 65)
            bt += 65;
        if(bt < 0)
            bt *= -1;
        if(bt > 90 && bt < 97)
            bt += 7;
        if(bt > 122)
            bt -= 5;
        if(bt == -128)
            bt = 122;
        return bt;
    }

    private byte[] truncateValues(String arg1, String arg2, int size)
    {
        byte result[] = new byte[size];
        byte value1[] = zipValues(arg1, size);
        byte value2[] = zipValues(arg2, size);
        for(int i = 0; i < size; i++)
            result[i] = (byte)((i + 1) * (value1[i] * 2 + value2[i] * 3));

        return result;
    }

    private byte[] zipValues(String args, int size)
    {
        byte result[] = new byte[size];
        for(int i = 0; i < size; i++)
            result[i] = 48;

        int pos = size - 1;
        for(int i = 0; i < args.length(); i++)
        {
            result[pos] += args.getBytes()[i];
            if(--pos < 0)
                pos = size - 1;
        }

        return result;
    }

    public static int INVALID_LICENSE = -1;
    public static int VALID_LICENSE = 0;
    public static int EXPIRED_LICENSE = 1;
    private String licenseKey;

}