How to read .pem file to get private and public key

Try this class.

package groovy;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.GeneralSecurityException;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.SignatureException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

import org.apache.commons.codec.binary.Base64;

public class RSA {

private static String getKey(String filename) throws IOException {
    // Read key from file
    String strKeyPEM = "";
    BufferedReader br = new BufferedReader(new FileReader(filename));
    String line;
    while ((line = br.readLine()) != null) {
        strKeyPEM += line + "\n";
    }
    br.close();
    return strKeyPEM;
}
public static RSAPrivateKey getPrivateKey(String filename) throws IOException, GeneralSecurityException {
    String privateKeyPEM = getKey(filename);
    return getPrivateKeyFromString(privateKeyPEM);
}

public static RSAPrivateKey getPrivateKeyFromString(String key) throws IOException, GeneralSecurityException {
    String privateKeyPEM = key;
    privateKeyPEM = privateKeyPEM.replace("-----BEGIN PRIVATE KEY-----\n", "");
    privateKeyPEM = privateKeyPEM.replace("-----END PRIVATE KEY-----", "");
    byte[] encoded = Base64.decodeBase64(privateKeyPEM);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(encoded);
    RSAPrivateKey privKey = (RSAPrivateKey) kf.generatePrivate(keySpec);
    return privKey;
}


public static RSAPublicKey getPublicKey(String filename) throws IOException, GeneralSecurityException {
    String publicKeyPEM = getKey(filename);
    return getPublicKeyFromString(publicKeyPEM);
}

public static RSAPublicKey getPublicKeyFromString(String key) throws IOException, GeneralSecurityException {
    String publicKeyPEM = key;
    publicKeyPEM = publicKeyPEM.replace("-----BEGIN PUBLIC KEY-----\n", "");
    publicKeyPEM = publicKeyPEM.replace("-----END PUBLIC KEY-----", "");
    byte[] encoded = Base64.decodeBase64(publicKeyPEM);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    RSAPublicKey pubKey = (RSAPublicKey) kf.generatePublic(new X509EncodedKeySpec(encoded));
    return pubKey;
}

public static String sign(PrivateKey privateKey, String message) throws NoSuchAlgorithmException, InvalidKeyException, SignatureException, UnsupportedEncodingException {
    Signature sign = Signature.getInstance("SHA1withRSA");
    sign.initSign(privateKey);
    sign.update(message.getBytes("UTF-8"));
    return new String(Base64.encodeBase64(sign.sign()), "UTF-8");
}


public static boolean verify(PublicKey publicKey, String message, String signature) throws SignatureException, NoSuchAlgorithmException, UnsupportedEncodingException, InvalidKeyException {
    Signature sign = Signature.getInstance("SHA1withRSA");
    sign.initVerify(publicKey);
    sign.update(message.getBytes("UTF-8"));
    return sign.verify(Base64.decodeBase64(signature.getBytes("UTF-8")));
}

public static String encrypt(String rawText, PublicKey publicKey) throws IOException, GeneralSecurityException {
    Cipher cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.ENCRYPT_MODE, publicKey);
    return Base64.encodeBase64String(cipher.doFinal(rawText.getBytes("UTF-8")));
}

public static String decrypt(String cipherText, PrivateKey privateKey) throws IOException, GeneralSecurityException {
    Cipher cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.DECRYPT_MODE, privateKey);
    return new String(cipher.doFinal(Base64.decodeBase64(cipherText)), "UTF-8");
}
}


Required jar library "common-codec-1.6"