cipher.. Won't work

[jgonzalez14]

I am trying to figure out why this cipher i have will not work. can anyone help?

import javax.swing.*;
public class Animal
{
    private String inputString;
    private int intOffset;
    
    public Animal()
    {
        inputString = null;
        intOffset = 0;
        
    }
    public static void main(String [] args)
    {
        Animal c2 = new Animal();
        int choose = JOptionPane.showConfirmDialog(null,"If you want to Encrypet Text Click (Yes) ,or Decrypt Click (No) or Cancel to exit :");
        
        if (choose == JOptionPane.YES_OPTION)
        {
            String plainText = c2.encrypt();
            JOptionPane.showMessageDialog(null,plainText);
        }
        else if(choose == JOptionPane.NO_OPTION)
        
        {
            String cipherText = c2.decrypt();
            JOptionPane.showMessageDialog(null,cipherText);
        }
        else
            System.exit(0);
    }
    
    public String encrypt()
    {
        inputString = ((String)JOptionPane.showInputDialog("Enter PlainText") ).toLowerCase().trim();
        intOffset = Integer.parseInt(JOptionPane.showInputDialog("Enter Key") );
        String letters = "abcdefghijklmnopqrstuvwxyz";
        StringBuffer sb = new StringBuffer();
        
        int holder = inputString.length();
        for(int i = 0; i < holder; i++)
            {
                String tmp = ""+inputString.charAt(i);
                int offset = letters.indexOf(tmp);
                offset += intOffset;
                if( offset > 25 ){
                    int newOffset = 0;
                    newOffset = offset % 26;
                    sb.append( letters.charAt(newOffset) );
                }
                else
                    {
                        sb.append( letters.charAt(offset) );
                    }
                    //
            }//forloop
            return sb.toString();
    }
    
    public String decrypt()
    {
        inputString = ((String)JOptionPane.showInputDialog("Enter CipherText") ).toLowerCase().trim();
        intOffset = Integer.parseInt(JOptionPane.showInputDialog("Enter Key") );
        String letters = "abcdefghijklmnopqrstuvwxyz";
        StringBuffer sb = new StringBuffer();
        
        int holder = inputString.length();
        for(int i = 0; i < holder; i++)
            {
                String tmp = ""+inputString.charAt(i);
                int offset = letters.indexOf(tmp);
                offset -= intOffset;
                
offset %= 26;
sb.append( letters.charAt(offset) );
            }
        return sb.toString();
    }
}

[Nicholas Jordan]

Study

import javax.crypto.Cipher;

and see if you can grasp any of it.

( no intent to be hard on you, it's just that this is what came to mind when I put your code in the editor to look at it... )