import java.security.NoSuchAlgorithmException;import java.security.SecureRandom;import javax.crypto.KeyGenerator;import javax.crypto.SecretKey;public class Test {  public static void main(String[] args) {    getKey();    getKeyByPass();  }  /**  * 隨機生成秘鑰  */  public static void getKey() {    try {      KeyGenerator kg = KeyGenerator.getInstance("AES");      kg.init(128);      //要生成多少位，只需要修改這里即可128, 192或256      SecretKey sk = kg.generateKey();      byte[] b = sk.getEncoded();      String s = byteToHexString(b);      System.out.println(s);      System.out.println("十六進制密鑰長度為"+s.length());      System.out.println("二進制密鑰的長度為"+s.length()*4);    }    catch (NoSuchAlgorithmException e) {      e.printStackTrace();      System.out.println("沒有此算法。");    }  }  /**  * 使用指定的字符串生成秘鑰  */  public static void getKeyByPass() {    //生成秘鑰    String password="testkey";    try {      KeyGenerator kg = KeyGenerator.getInstance("AES");      // kg.init(128);//要生成多少位，只需要修改這里即可128, 192或256      //SecureRandom是生成安全隨機數序列，password.getBytes()是種子，只要種子相同，序列就一樣，所以生成的秘鑰就一樣。      kg.init(128, new SecureRandom(password.getBytes()));      SecretKey sk = kg.generateKey();      byte[] b = sk.getEncoded();      String s = byteToHexString(b);      System.out.println(s);      System.out.println("十六進制密鑰長度為"+s.length());      System.out.println("二進制密鑰的長度為"+s.length()*4);    }    catch (NoSuchAlgorithmException e) {      e.printStackTrace();      System.out.println("沒有此算法。");    }  }  /**  * byte數組轉化為16進制字符串  * @param bytes  * @return  */  public static String byteToHexString(byte[] bytes) {    StringBuffer sb = new StringBuffer();    for (int i = 0; i < bytes.length; i++) {      String strHex=Integer.toHexString(bytes[i]);      if(strHex.length() > 3) {        sb.append(strHex.substring(6));      } else {        if(strHex.length() < 2) {          sb.append("0" + strHex);        } else {          sb.append(strHex);        }      }    }    return sb.toString();  }}