EOFException while calling ObjectInputStream.readObject()

I need to get a hashmap from a hex string I’ve serialized. Currently, I can get the hashmap, but it creates an EOFException.

• private static StringwriteMaterialMap(HashMap<String, Double> map) throws Exception {

  System.out.print(map);

  ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
  ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);

  objectOutputStream.writeObject(map);
  objectOutputStream.close();

  byte[] bytes = byteArrayOutputStream.toByteArray();

  final StringBuilder stringBuilder = new StringBuilder();
  for (byte bytte : bytes) {
  stringBuilder.append(String.format("%02x", bytte));
  }

  System.out.print("Saving: " + stringBuilder.toString());

  return stringBuilder.toString();
  }

  @SuppressWarnings("unchecked")
  private static HashMap<String, Double> readMaterialMap(String hex) throws Exception {

  int length = hex.length();
  byte[] byteArray = new byte[length / 2];
  for (int i = 0; i < length; i += 2) {
  byteArray[i / 2] = (byte) ((Character.digit(hex.charAt(i), 16) << 4)
  + Character.digit(hex.charAt(i + 1), 16));
  }

  ObjectInputStream objectInputStream = new ObjectInputStream(new ByteArrayInputStream(byteArray));
  System.out.print(objectInputStream.readObject());

  HashMap<String, Double> materials = new HashMap<>((Map<String, Double>) objectInputStream.readObject());

  System.out.print(materials);

  return materials;

  }


Currently, I get this:

{"A"=1}
{}
java.io.EOFException
    at java.io.ObjectInputStream$BlockDataInputStream.peekByte
    at java.io.ObjectInputStream.readObject0
    at java.io.ObjectInputStream.readObject
    at me.MapHex.readMaterialMap(MineHex.java:66)

What I can see from this is: It can read the object, but the EOFE is preventing me from casting it to a HashMap. I need to cast it to a HashMap without an EOFE