Shuffling character array in Java producing NullPointerException

I'm trying to create word encrypted and decrypter using Java. Having initialized a char array of the alphabet, I'm attempting to shuffle it (and create the crypt code) by copying into another array of Character class in order to do Collections.shuffle. I don't get any compilation errors, but get a NullPointerException when attempting to run the code. Do let me know if you have any insight into my issue:

my Cryptogram constructor to shuffle the alphabet:

public class Cryptogram {
  private char [] alphabet = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u','v', 'w', 'x', 'y', 'z' };
  private char [] cryptCode;

  public Cryptogram( ) {
    cryptCode = new char[alphabet.length];

    Character[] anAlphabet = new Character[alphabet.length];
    for (int i = 0; i < alphabet.length; i++) {
      alphabet[i] = anAlphabet[i];
    }

    List<Character> cryptList = Arrays.asList(anAlphabet);
    Collections.shuffle(cryptList);

    Object ob[] = cryptList.toArray();

    for (int j = 0; j < anAlphabet.length; j++){
      cryptCode[j] = anAlphabet[j];
    }

  }

my user input class:

import java.util.Scanner;

public class CryptogramClient {
  public static void main( String [] args ) {
    Cryptogram cg = new Cryptogram( );
    System.out.println( cg ); // print alphabet and substitution code
  }
}

Exception:

java.lang.NullPointerException
at Cryptogram.<init>(Cryptogram.java:39)
at CryptogramClient.main(CryptogramClient.java:16)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:272)