Thread: Can you tell me what this code do ?

Hey guys, first off i'm new here and i'm also new at java programming, i know the basics so far but to me it is just super complicated compared to the language i used before (Visual Basic) but i'm actually trying to learn Java since everybody told me it is way better than VB so i thought i'd give it a try, i've bought the book "Java programming for dummies" and to be perfectly honest it's not what i expected, i mean it does teach you the basic stuff of Java programming such as operators, statements and etc but when trying to "read" a source code and try to understand it, i tend to get headaches more than anything else for example, i am trying to make an encryption/decryption program as my first Java program so i've downloaded a few source codes demonstrating encryption algorythms and i'm trying to get what exactly the code do and how do i use it

Here's the actual code:



P.S Sorry if i didn't post this in the right section

 
import java.io.*;
 
public final class qb extends FilterOutputStream
    implements DataOutput
{
 
    public qb(OutputStream outputstream)
    {
        super(outputstream);
        b = 0;
        c = new byte[8];
    }
 
    public final synchronized void write(int i)
        throws IOException
    {
        if(a != null && a.length > 0)
            i ^= a[q()];
        super.out.write(i);
    }
 
    public final void q(byte abyte0[])
    {
        a = abyte0;
        b = 0;
    }
 
    private int q()
    {
        b = (b + 1) % a.length;
        return b;
    }
 
    public final void flush()
        throws IOException
    {
        super.out.flush();
    }
 
    public final void writeDouble(double d)
        throws IOException
    {
        writeLong(Double.doubleToLongBits(d));
    }
 
    public final void writeFloat(float f)
        throws IOException
    {
        writeInt(Float.floatToIntBits(f));
    }
 
    public final void writeByte(int i)
        throws IOException
    {
        write(i);
    }
 
    public final void writeChar(int i)
        throws IOException
    {
        write(i >>> 8 & 0xff);
        write(i >>> 0 & 0xff);
    }
 
    public final void writeInt(int i)
        throws IOException
    {
        write(i >>> 24 & 0xff);
        write(i >>> 16 & 0xff);
        write(i >>> 8 & 0xff);
        write(i >>> 0 & 0xff);
    }
 
    public final void writeShort(int i)
        throws IOException
    {
        write(i >>> 8 & 0xff);
        write(i >>> 0 & 0xff);
    }
 
    public final void writeLong(long l)
        throws IOException
    {
        c[0] = (byte)(int)(l >>> 56);
        c[1] = (byte)(int)(l >>> 48);
        c[2] = (byte)(int)(l >>> 40);
        c[3] = (byte)(int)(l >>> 32);
        c[4] = (byte)(int)(l >>> 24);
        c[5] = (byte)(int)(l >>> 16);
        c[6] = (byte)(int)(l >>> 8);
        c[7] = (byte)(int)(l >>> 0);
        write(c, 0, 8);
    }
 
    public final void writeBoolean(boolean flag)
        throws IOException
    {
        write(flag ? 1 : 0);
    }
 
    public final synchronized void write(byte abyte0[], int i, int j)
        throws IOException
    {
        if((i | j | abyte0.length - (j + i) | i + j) < 0)
            throw new IndexOutOfBoundsException();
        for(int k = 0; k < j; k++)
            write(abyte0[i + k]);
 
    }
 
    public final void write(byte abyte0[])
        throws IOException
    {
        write(abyte0, 0, abyte0.length);
    }
 
    public final void writeBytes(String s)
        throws IOException
    {
        int i = s.length();
        for(int j = 0; j < i; j++)
            write((byte)s.charAt(j));
 
    }
 
    public final void writeChars(String s)
        throws IOException
    {
        int i = s.length();
        for(int j = 0; j < i; j++)
        {
            char c1 = s.charAt(j);
            write(c1 >>> 8 & 0xff);
            write(c1 >>> 0 & 0xff);
        }
 
    }
 
    public final void writeUTF(String s)
        throws IOException
    {
        q(s, this);
    }
 
    private static int q(String s, DataOutput dataoutput)
        throws IOException
    {
        int i = s.length();
        int j = 0;
        char ac[] = new char[i];
        int k = 0;
        s.getChars(0, i, ac, 0);
        for(int l = 0; l < i; l++)
        {
            char c1;
            if((c1 = ac[l]) >= '\001' && c1 <= '\177')
            {
                j++;
                continue;
            }
            if(c1 > '\u07FF')
                j += 3;
            else
                j += 2;
        }
 
        if(j > 65535)
            throw new UTFDataFormatException();
        k++;
        byte abyte0[];
        (abyte0 = new byte[j + 2])[0] = (byte)(j >>> 8 & 0xff);
        k++;
        abyte0[1] = (byte)(j >>> 0 & 0xff);
        for(int i1 = 0; i1 < i; i1++)
        {
            char c2;
            if((c2 = ac[i1]) >= '\001' && c2 <= '\177')
            {
                abyte0[k++] = (byte)c2;
                continue;
            }
            if(c2 > '\u07FF')
            {
                abyte0[k++] = (byte)(0xe0 | c2 >> 12 & 0xf);
                abyte0[k++] = (byte)(0x80 | c2 >> 6 & 0x3f);
                abyte0[k++] = (byte)(0x80 | c2 >> 0 & 0x3f);
            } else
            {
                abyte0[k++] = (byte)(0xc0 | c2 >> 6 & 0x1f);
                abyte0[k++] = (byte)(0x80 | c2 >> 0 & 0x3f);
            }
        }
 
        dataoutput.write(abyte0);
        return j + 2;
    }
 
    private byte a[];
    private int b;
    private byte c[];
}

Apparently, this is supposed to encrypt data, but the problem is i don't know how to call the main function of that code

If any of you guys, understand what this code do, could you please explain to me how i can use it

Your help is very appreciated, thank you

- John