polyalphabetic J# Code

This is a polyalphabetic Security Algorithm(polyalphabetic cipher decryption and encryption) i made using J# (close to C#) .Download the Code and enjoy .You must have the virtual machine installed on your PC to run this code.
csharp code

package ployalphapetic;

import System.Collections.Generic.*;
import System.Data.*;
import System.Drawing.*;
import System.ComponentModel.*;
import System.Windows.Forms.*;
import System.Collections.ArrayList;

/**
 * Summary description for Form1.
 */
public class Form1 extends System.Windows.Forms.Form
{
	private TextBox textBox1;
	private TextBox textBox2;
	private Label label1;
	private Label label2;
	private Label label3;
	private TextBox textBox3;
	private Button button1;
	private Button button2;
//	ArrayList letter = new ArrayList();
	char[] letter = new char[26];
	final static int addnumber = 97;
	String pureplaintxt="";
	String ciphertxt = "";
	private Timer timer1;
	/**
	 * Required designer variable.
	 */
	private System.ComponentModel.IContainer components;

	public Form1()
	{
		//
		// Required for Windows Form Designer support
		//
		InitializeComponent();

		//
		// TODO: Add any constructor code after InitializeComponent call
		//
	}

	#region Windows Form Designer generated code
	/**
     * Clean up any resources being used.
     */
	protected void Dispose(boolean disposing)
	{
		if (disposing)
		{
			if (components != null)
			{
				components.Dispose();
			}
		}
		super.Dispose(disposing);
	}

	/**
	 * Required method for Designer support - do not modify
	 * the contents of this method with the code editor.
	 */
	private void InitializeComponent()
	{
		this.components = new System.ComponentModel.Container();
		this.textBox1 = new System.Windows.Forms.TextBox();
		this.textBox2 = new System.Windows.Forms.TextBox();
		this.label1 = new System.Windows.Forms.Label();
		this.label2 = new System.Windows.Forms.Label();
		this.label3 = new System.Windows.Forms.Label();
		this.textBox3 = new System.Windows.Forms.TextBox();
		this.button1 = new System.Windows.Forms.Button();
		this.button2 = new System.Windows.Forms.Button();
		this.timer1 = new System.Windows.Forms.Timer(this.components);
		this.SuspendLayout();
		// 
		// textBox1
		// 
		this.textBox1.set_Location(new System.Drawing.Point(73, 25));
		this.textBox1.set_Name("textBox1");
		this.textBox1.set_Size(new System.Drawing.Size(207, 20));
		this.textBox1.set_TabIndex(0);
		// 
		// textBox2
		// 
		this.textBox2.set_Location(new System.Drawing.Point(73, 64));
		this.textBox2.set_Multiline(true);
		this.textBox2.set_Name("textBox2");
		this.textBox2.set_Size(new System.Drawing.Size(207, 77));
		this.textBox2.set_TabIndex(1);
		// 
		// label1
		// 
		this.label1.set_AutoSize(true);
		this.label1.set_Location(new System.Drawing.Point(12, 28));
		this.label1.set_Name("label1");
		this.label1.set_Size(new System.Drawing.Size(41, 13));
		this.label1.set_TabIndex(2);
		this.label1.set_Text("Key   : ");
		// 
		// label2
		// 
		this.label2.set_AutoSize(true);
		this.label2.set_Location(new System.Drawing.Point(12, 68));
		this.label2.set_Name("label2");
		this.label2.set_Size(new System.Drawing.Size(59, 13));
		this.label2.set_TabIndex(3);
		this.label2.set_Text("Plain text :");
		// 
		// label3
		// 
		this.label3.set_AutoSize(true);
		this.label3.set_Location(new System.Drawing.Point(12, 158));
		this.label3.set_Name("label3");
		this.label3.set_Size(new System.Drawing.Size(108, 13));
		this.label3.set_TabIndex(4);
		this.label3.set_Text("Encrypted message :");
		// 
		// textBox3
		// 
		this.textBox3.set_Location(new System.Drawing.Point(73, 182));
		this.textBox3.set_Multiline(true);
		this.textBox3.set_Name("textBox3");
		this.textBox3.set_Size(new System.Drawing.Size(207, 112));
		this.textBox3.set_TabIndex(5);
		// 
		// button1
		// 
		this.button1.set_Location(new System.Drawing.Point(205, 312));
		this.button1.set_Name("button1");
		this.button1.set_Size(new System.Drawing.Size(75, 23));
		this.button1.set_TabIndex(6);
		this.button1.set_Text("Encrypte");
		this.button1.set_UseVisualStyleBackColor(true);
		this.button1.add_Click(new System.EventHandler(this.button1_Click));
		// 
		// button2
		// 
		this.button2.set_Location(new System.Drawing.Point(91, 312));
		this.button2.set_Name("button2");
		this.button2.set_Size(new System.Drawing.Size(75, 23));
		this.button2.set_TabIndex(7);
		this.button2.set_Text("Decrypte");
		this.button2.set_UseVisualStyleBackColor(true);
		this.button2.add_Click(new System.EventHandler(this.button2_Click));
		// 
		// timer1
		// 
		this.timer1.set_Enabled(true);
		this.timer1.add_Tick(new System.EventHandler(this.timer1_Tick));
		// 
		// Form1
		// 
		this.set_AutoScaleDimensions(new System.Drawing.SizeF(6F, 13F));
		this.set_AutoScaleMode(System.Windows.Forms.AutoScaleMode.Font);
		this.set_ClientSize(new System.Drawing.Size(292, 383));
		this.get_Controls().Add(this.button2);
		this.get_Controls().Add(this.button1);
		this.get_Controls().Add(this.textBox3);
		this.get_Controls().Add(this.label3);
		this.get_Controls().Add(this.label2);
		this.get_Controls().Add(this.label1);
		this.get_Controls().Add(this.textBox2);
		this.get_Controls().Add(this.textBox1);
		this.set_ForeColor(System.Drawing.Color.get_Blue());
		this.set_FormBorderStyle(System.Windows.Forms.FormBorderStyle.FixedSingle);
		this.set_MaximizeBox(false);
		this.set_Name("Form1");
		this.set_StartPosition(System.Windows.Forms.FormStartPosition.CenterScreen);
		this.set_Text("Polyalphabetic");
		this.add_FormClosing(new System.Windows.Forms.FormClosingEventHandler(this.Form1_FormClosing));
		this.add_Load(new System.EventHandler(this.Form1_Load));
		this.ResumeLayout(false);
		this.PerformLayout();

	}
	#endregion

	private void Form1_Load(Object sender, System.EventArgs e)
	{
		for (int i = 0; i < 26; i++)
		{
			letter[i] = (char)(i + addnumber);
		}
	}

	private void button1_Click(Object sender, System.EventArgs e)
	{
				//	textBox1   which have the key
				//	textBox2   which have plain text
				//	textBox3   which have encrypted message
		textBox3.set_Enabled(true);
		textBox2.set_Enabled(false);
		textBox1.set_Enabled(false);
		textBox3.set_Text("");
		String key = textBox1.get_Text();
		for (int i = 0; i < textBox2.get_Text().length(); i++)
		{
			if (!(textBox2.get_Text().substring(i,i+1).Equals(" ")))
			{
				pureplaintxt += textBox2.get_Text().substring(i, i+1);
			}
 		}
		while (textBox1.get_Text().length() < pureplaintxt.length())
		{
			textBox1.set_Text(textBox1.get_Text() + key);
		}
		textBox1.set_Text(textBox1.get_Text().substring(0,pureplaintxt.length()));
		key = textBox1.get_Text();
		encrypte();
		key = "";
		pureplaintxt = "";
	}
	public void encrypte()
	{
		String keyletter;
		String plaintxtletter;
		int keyindex = 0 ;
		int plaintxtindex=0;
		int cipherindex=0;

		//////// To get letter by letter from key and pure plain text /////// 

		for (int i = 0; i < pureplaintxt.length(); i++)
		{
			keyletter = textBox1.get_Text().substring(i, i + 1);
			plaintxtletter = pureplaintxt.substring(i, i + 1);

	    ///	To search inside the array letter with key letter and plain text letter ///

			for (int j = 0; j < letter.length; j++)
			{
				if (keyletter.toCharArray()[0]==letter[j])
				{
					keyindex = j;
				}
				if (plaintxtletter.toCharArray()[0] == letter[j])
				{
					plaintxtindex = j;
				}
			}
			cipherindex = (keyindex + plaintxtindex) % 26;
			textBox3.set_Text(textBox3.get_Text()+letter[cipherindex]);
		}
	}

	private void button2_Click(Object sender, System.EventArgs e)
	{
		textBox2.set_Enabled(true);
		textBox3.set_Enabled(false);
		textBox1.set_Enabled(false);
		textBox2.set_Text("");
		String key = textBox1.get_Text();
		for (int i = 0; i < textBox3.get_Text().length(); i++)
		{
			if (!(textBox3.get_Text().substring(i, i + 1).Equals(" ")))
			{
				ciphertxt += textBox3.get_Text().substring(i, i + 1);
			}
		}
		while (textBox1.get_Text().length() < ciphertxt.length())
		{
			textBox1.set_Text(textBox1.get_Text() + key);
		}
		textBox1.set_Text(textBox1.get_Text().substring(0, ciphertxt.length()));
		key = textBox1.get_Text();
		decrypte();
		key = "";
		ciphertxt = "";
	}
	public void decrypte()
	{
		String keyletter;
		String cipherletter;
		int keyindex = 0;
		int cipherindex = 0;
		int plaintxtindex = 0;
		int check = 0;
		//////// To get letter by letter from key and pure plain text /////// 

		for (int i = 0; i < ciphertxt.length(); i++)
		{
			keyletter = textBox1.get_Text().substring(i, i + 1);
			cipherletter = ciphertxt.substring(i, i + 1);

			///	To search inside the array letter with key letter and plain text letter ///

			for (int j = 0; j < letter.length; j++)
			{
				if (keyletter.toCharArray()[0] == letter[j])
				{
					keyindex = j;
				}
				if (cipherletter.toCharArray()[0] == letter[j])
				{
					cipherindex = j;
				}
			}
			check = cipherindex - keyindex;
			if (check < 0)
			{
				check = 26 - (keyindex - cipherindex);
				plaintxtindex = check % 26;
				textBox2.set_Text(textBox2.get_Text() + letter[plaintxtindex]);
			}
			else
			{
				plaintxtindex = check % 26;
				textBox2.set_Text(textBox2.get_Text() + letter[plaintxtindex]);
			}
		}
	}

	private void Form1_FormClosing(Object sender, FormClosingEventArgs e)
	{
		DialogResult exit;
		exit = MessageBox.Show("Are u sure ?         ", "Exit",MessageBoxButtons.YesNo);
		if (exit == DialogResult.Yes)
		{
			MessageBox.Show("Thanks for using my program           ", "Goooooooooooood bye");
			Application.ExitThread();
		}
		else
		{
			e.set_Cancel(true);
		}
	}

	private void timer1_Tick(Object sender, System.EventArgs e)
	{
	}
}

thx useful

updated.