Read RSA key from file

KeyReader

package com.punchouty.ed;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

public class KeyReader {
		
	public static final String BASE_FOLDER = "keys/";
	public static final String PRIVATE_KEY_FILE_NAME = "private.key";
	public static final String PUBLIC_KEY_FILE_NAME = "public.key";
	public static final String PRIVATE_KEY_FILE = BASE_FOLDER + PRIVATE_KEY_FILE_NAME;
	public static final String PUBLIC_KEY_FILE = BASE_FOLDER + PUBLIC_KEY_FILE_NAME;
	public static final String KEY_GENERATION_ALGORITHM = "RSA";
	public static final String ENCRYPTION_DECRYPTION_ALGORITHM = "RSA/ECB/PKCS1Padding";
	
	public PrivateKey readPrivateKey() throws IOException, NoSuchAlgorithmException, InvalidKeySpecException{
		File keyFile = new File(PRIVATE_KEY_FILE);
		boolean exists = keyFile.exists();
		if(exists) {
			FileInputStream fis = new FileInputStream(keyFile);
			byte[] encodedPrivateKey = new byte[(int) keyFile.length()];
			fis.read(encodedPrivateKey);
			fis.close();
			
			KeyFactory keyFactory = KeyFactory.getInstance(KEY_GENERATION_ALGORITHM);
			PKCS8EncodedKeySpec privateKeySpec = new PKCS8EncodedKeySpec(
					encodedPrivateKey);
			PrivateKey privateKey = keyFactory.generatePrivate(privateKeySpec);
			System.out.println("Read Private Key successfully: " + getHexString(privateKey.getEncoded()));
			return privateKey;
		}
		else {
			System.err.println("File " + keyFile + " does not exists. Hence exiting");
			System.exit(0);
		}
		return null;
	}
	
	public PublicKey readPublicKey() throws IOException, NoSuchAlgorithmException, InvalidKeySpecException{
		File keyFile = new File(PUBLIC_KEY_FILE);
		boolean exists = keyFile.exists();
		if(exists) {
			FileInputStream fis = new FileInputStream(keyFile);
			byte[] encodedPublicKey = new byte[(int) keyFile.length()];
			fis.read(encodedPublicKey);
			fis.close();
			KeyFactory keyFactory = KeyFactory.getInstance(KEY_GENERATION_ALGORITHM);
			X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(
					encodedPublicKey);
			PublicKey publicKey = keyFactory.generatePublic(publicKeySpec);
			System.out.println("Read Public Key successfully: " + getHexString(publicKey.getEncoded()));
			return publicKey;
		}
		else {
			System.err.println("File " + keyFile + " does not exists. Hence exiting");
			System.exit(0);
		}
		return null;
	}
	
	public static final String getHexString(byte[] b) {
		String result = "";
		for (int i = 0; i < b.length; i++) {
			result += Integer.toString((b[i] & 0xff) + 0x100, 16).substring(1);
		}
		return result;
	}
}