* If you want to...

• 1. Write to a new file = FileWriter
  FileWriter fw = new FileWriter(file);
• 2. Use the buffer, then write to the file = BufferedWriter
  BufferedWriter bw = new BufferedWriter(new FileWriter(file));
• 3. Use the buffer, then write to the file, though use methods such as println() = PrintWriter
  PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter(file)));

1. If you use BufferedWriter, you cannot use a line separator.
2. If you then use PrintWriter as a wrapper around BufferedWriter, you can then use the line separator again

It is legal to serialize an object of a type that has a supertype that does NOT implement java.io.Serializable.

+--+
+--+ int good = 3
Vehicle

 +--+ extends Vehicle (Serializable)
 +--+ int juice = 5
 Van

If you create an instance of the object and you intend to serialize it, make sure you 'implement serializable'. Classes cannot be serialized if it doesn't implement the interface Serializable Java I/O Fundamentals + Video

Issue with serializable with inherited class
+--+ Serializable
+--+ int good 3
food

 +--+ extends food
 +--+ int juice 5
 fruit

  +--+ extends fruit
  +--+ int yellow 4
  Banana

* Obj serialized by one JVM can be deserialized by another JVM

* The first superclass in the hierarchy of a serializable class MUST have a non-argument constructor If violated, and you run the readObject(), you will receive an InvalidClassException in runtime

* When the object instance is de-serialized, the superclass constructor will run again

* The constructor of the object instance will not run when it's de-serialized

* Static fields are not serializable

When you de-serialize with multiple attributes,it has to be in order

public int x, y

you realize it!
De-serialize it! (see below)
public void readObject(ObjectInputStream s){
x = s.readInt(); y = s.readInt();
}

NOTE: y = s.readInt(); x = s.readInt();

When the object instance is de-serialized, the superclass constructor will run again
+--+ Vehicle(){
+--+ System.out.println("1")}
Vehicle

 +--+ extends Vehicle (Serializable)
 +--+ Van(){System.out.println("0")}
 Van

1. new instance of Van
2. serialize then de-serialized
3. Printed out = 101

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