Why is implementing the Parcelable interface necessary in Android objects?

The Parcelable interface in Android is used for efficient serialization of objects so that they can be transferred between application components (for example, between Activity or Service) via Intent or to save state.

The need to implement Parcelable instead of standard serialization (Serializable) is due to:

• Performance: Parcelable works faster and requires fewer resources because it is optimized for Android.
• Control: the developer explicitly describes how the object is serialized and deserialized, which reduces errors and increases efficiency.

A simple implementation example:

public class User implements Parcelable {
    private String name;
    private int age;

    protected User(Parcel in) {
        name = in.readString();
        age = in.readInt();
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(name);
        dest.writeInt(age);
    }

    @Override
    public int describeContents() {
        return 0;
    }

    public static final Creator<User> CREATOR = new Creator<User>() {
        @Override
        public User createFromParcel(Parcel in) {
            return new User(in);
        }

        @Override
        public User[] newArray(int size) {
            return new User[size];
        }
    };
}

Thus, Parcelable provides an efficient mechanism for data transfer between Android components.