Encrypting Message Using RSA Algorithm - Invalid Stream Header Error

I am trying to encrypt a message using RSA algo but getting the following error:

java.io.StreamCorruptedException: invalid stream header
at java.io.ObjectInputStream.readStreamHeader(ObjectI nputStream.java:753)
at java.io.ObjectInputStream.<init>(ObjectInputStream .java:268)

Java Code :

public static final String PUBLIC_KEY_FILE = "C:/TXT.key"; 
final String originalText = "Text to be encrypted ";
ObjectInputStream inputStream = null;
FileInputStream f= new FileInputStream(PUBLIC_KEY_FILE);
// getting error on the below line
inputStream = new ObjectInputStream(f);
final PublicKey publicKey = (PublicKey) inputStream.readObject();
final byte[] cipherText = encrypt(originalText, publicKey);