Unchecked cast java.io.Serializable to java.util.ArrayList

Question

Help please, I get the following message, in the following code that I have:

listaFinal = (ArrayList<PuntoNota>) getIntent().getSerializableExtra("miLista");

AdapterDatos adapter = new AdapterDatos(this, listaFinal);

PuntoNota.java

public class PuntoNota implements Serializable{
private String punto;
private String nota;

public PuntoNota (String punto, String nota){
    this.punto = punto;
    this.nota = nota;
}

public String getPunto(){
    return punto;
}


public String getNota(){
    return nota;
}

}

AdapterDatos:

public AdapterDatos(Context context, ArrayList<PuntoNota> puntoNotaList) {
    this.context = context;
    this.puntoNotaList = puntoNotaList;
}

The application is working well, but I get the following message:

Unchecked cast: 'java.io.Serializable' to 'java.util.ArrayList ' less ... (Ctrl + F1).
about this code: (ArrayList ) getIntent (). getSerializableExtra ("myList"); will it be advisable to delete or hide this message?

@MạnhQuyếtNguyễn but solving cast from serializable to the respective desired generic list will add to good coding practices. Otherwise, when you use Parcelable, data types are known in advance at both ends, and this issue is resolved. — Abhinav Saxena
– Abhinav Saxena, Commented Dec 8, 2021 at 7:35
it happens to warn about usage, not for compile code checking. Your solution only hide it, not solve it either. so live with it unless changing to type safe serializable — Mạnh Quyết Nguyễn
– Mạnh Quyết Nguyễn, Commented Dec 14, 2021 at 16:26

Son Truong · Accepted Answer · 2018-08-13 04:09:55Z

Root cause: This is a warning from IDE, getSerializableExtra return a Serializable, and you are trying to convert to ArrayList<PuntoNota>. It might throw ClassCastException at runtime if the programe cannot cast it to your expected type.

Solution: In android to pass a user-defined object around, your class should implements Parcelable instead of Serializable interface.

class PuntoNota implements Parcelable {
    private String punto;
    private String nota;

    public PuntoNota(String punto, String nota) {
        this.punto = punto;
        this.nota = nota;
    }

    protected PuntoNota(Parcel in) {
        punto = in.readString();
        nota = in.readString();
    }

    public String getPunto() {
        return punto;
    }

    public String getNota() {
        return nota;
    }

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

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(punto);
        dest.writeString(nota);
    }

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

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

At sender side

ArrayList<PuntoNota> myList = new ArrayList<>();
// Fill data to myList here
...
Intent intent = new Intent();
intent.putParcelableArrayListExtra("miLista", myList);

At receiver side

ArrayList<? extends PuntoNota> listaFinal = getIntent().getParcelableArrayListExtra("miLista");

Anisuzzaman Babla · Accepted Answer · 2018-08-12 05:10:20Z

12

You can set a warning Suppression @SuppressWarnings annotation.

Example:

@SuppressWarnings("unchecked")
listaFinal = (ArrayList<PuntoNota>) getIntent().getSerializableExtra("miLista");

It is an annotation to suppress compile warnings about unchecked generic operations (not exceptions), such as casts. It essentially implies that the programmer did not wish to be notified about these which he is already aware of when compiling a particular bit of code.

You can read more on this specific annotation here:

SuppressWarnings

Additionally, Oracle provides some tutorial documentation on the usage of annotations here:

Annotations

As they put it,

"The 'unchecked' warning can occur when interfacing with legacy code written before the advent of generics (discussed in the lesson titled Generics)."

answered Aug 12, 2018 at 5:10

Anisuzzaman Babla

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2 Comments

AlexS Over a year ago

My eyes are relaxed now by this trick, thank you. Also you should put @SuppressWarnings("unchecked") right above your method

Abhinav Saxena Over a year ago

You can put it above class declaration as well. It will remove all the warnings related to this.

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