By design, the ArrayList class in Java is serializable by default. This means you don't need to implement any special interfaces to write an ArrayList to a byte stream using ObjectOutputStream . The real catch is that every inside that list must also implement java.io.Serializable . If even one object in a list of thousands fails this requirement, the entire process crashes with a NotSerializableException . The "Disaster" of Java Serialization
Because of these flaws, the Android ecosystem has largely moved toward more specialized solutions: Android Java Serialize Arraylist
Deserializing data from an untrusted source is a major security vulnerability, as it allows for the reconstruction of complex object graphs without proper validation. By design, the ArrayList class in Java is