Calculate memory of a Map Entry

Question

I have a Map(String, String) and I want to find the memory size of an Entry and the Map in total. I read somewhere that Instrumentation might be useful (Instrumentation). Do

Answer 1

Use ObjectOutputStream to write the object to a ByteArrayOutputstream and check the length of the resultant byte array.

Obviously your Map.Entry will need to implement Serializable.

public int getSizeInBytes(Serializable someObject) {
    ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
    ObjectOutputStream objectOut = new ObjectOutputStream(byteOut);
    objectOut.writeObject(someObject);
    objectOut.flush();
    return byteOut.toByteArray().length;
}

public int getSizeBits(Serializable someObject) {
    return getSizeInBytes(someObject) * 8;
}