KeyLengthDetector.java

import javax.crypto.Cipher;
import java.security.NoSuchAlgorithmException;

public class KeyLengthDetector {
  public static void main(String[] args) {
    String transformation = "AES";
    if (args.length >= 1) transformation = args[0];
    int allowedKeyLength = 0;

    try {
      allowedKeyLength = Cipher.getMaxAllowedKeyLength(transformation);
    } catch (NoSuchAlgorithmException e) {
      e.printStackTrace();
    }

    System.out.println("The allowed key length for " + transformation + " is: " + allowedKeyLength);
    Cipher.getInstance(transformation);
  }
}