what is this error on open declaration?

   KeyGenerator kgen = KeyGenerator.getInstance("AES");
   kgen.init(128); // 192 and 256 bits may not be available

In eclipse when I select KeyGenerator and right click open declaration I get a window opened.

click here to see error image (Image link broken)

Can you explain whats wrong here ? btw here is the complete code

package org.temp2.cod1;

import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.io.*;

/**
* This program generates a AES key, retrieves its raw bytes, and
* then reinstantiates a AES key from the key bytes.
* The reinstantiated key is used to initialize a AES cipher for
* encryption and decryption.
*/

public class AES1
{

    /**
    * Turns array of bytes into string
    *
    * @param buf    Array of bytes to convert to hex string
    * @return   Generated hex string
    */
    public static String asHex (byte buf[])
    {
        StringBuffer strbuf = new StringBuffer(buf.length * 2);
        int i;

        for (i = 0; i < buf.length; i++)
        {
            if (((int) buf[i] & 0xff) < 0x10)
                strbuf.append("0");

            strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
        }

        return strbuf.toString();
    }

    public static void main(String[] args) throws Exception
    {

        String message="This is just an example";

        // Get the KeyGenerator

        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        kgen.init(128); // 192 and 256 bits may not be available


        // Generate the secret key specs.
        SecretKey skey = kgen.generateKey();
        byte[] raw = skey.getEncoded();

        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");


        // Instantiate the cipher

        Cipher cipher = Cipher.getInstance("AES");

        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);

        byte[] encrypted =
        cipher.doFinal((args.length == 0 ?
        "This is just an example" : args[0]).getBytes());
        System.out.println("encrypted string: " + asHex(encrypted));

        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        byte[] original =
        cipher开发者_如何学运维.doFinal(encrypted);
        String originalString = new String(original);
        System.out.println("Original string: " +
        originalString + " " + asHex(original));
    }
}

It's just showing that the source to the KeyGenerator class isn't shipped with the JDK - presumably it would violate export restrictions or something similar. (I get the same message on my Eclipse installation too, despite other classes displaying source with no problems, so I suspect it's not a configuration issue.)

Do you really need to see the source to KeyGenerator? What were you trying to find out?