Thread: Passing an array to the constructor!

I implemented RC4 cryptography algorithm using Java but I still don't know why it doesn't work when I try to pass an array from main method to the constructor! How can I make it works?
Thank you in advance

 
package rc4.generator;
 
 
public class RC4_Generator {
    private int[] S;
    private int[] T;
    private int keylen;    
 
    public RC4_Generator(byte[] key) throws Exception 
    {
            if (key.length < 1 || key.length > 256) 
            	throw new Exception("The key should be between 1 to 256 Byte!"); 
            else 
            	// The initialization of both S[] and T[].
            {
                    keylen = key.length;
                    for (int i = 0; i < 256; i++) {
                            S[i] = i;
                            T[i] = key[i % keylen];
            }
 
                // The S permutation.
                    int j = 0;
                    for (int i = 0; i < 256; i++) 
                    {
                            j = (j + S[i] + T[i]) % 256;
                            S[i] = S[i] ^ S[j];
                            S[j] = S[j] ^ S[i];
                            S[i] = S[i] ^ S[j];
                    }
            }
    }
 
 
    public int[] encryption(int[] plaintext) 
    {
            int[] ciphertext = new int[plaintext.length];
            int i = 0, j = 0, k, t;
            for (int c = 0; c < plaintext.length; c++) {
                    i = (i + 1) % 256;
                    j = (j + S[i]) % 256;
                    S[i] = S[i] ^ S[j];
                    S[j] = S[j] ^ S[i];
                    S[i] = S[i] ^ S[j];
                    t = (S[i] + S[j]) % 256;
                    k = S[t];
                    //ciphertext[c] = plaintext[c] ^ k;
            }
            return ciphertext;
    }
 
 
    public static void main(String[] args){
 
    	byte[] k ={0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30};
 
    	RC4_Generator rc4= new RC4_Generator(k);
    }
 
}

Oh! I'm sorry for that! I'm a new user here! I will be clear

I got this error:
-----------------------------------------------------------------
Exception in thread "main" java.lang.NullPointerException
at rc4.generator.RC4_Generator.<init>(RC4_Generator.j ava:18)
at rc4.generator.RC4_Generator.main(RC4_Generator.jav a:62)
----------------------------------------------------------------
Do you see guys why? I try to understand it but I couldn't!

It worked!
Thank you so much (aussiemcgr ) for your help! Really Appreciate that