Casting ArrayList class variables for deserialization

Question

I am trying to deserialize a single variable in java however seem to be bumping into a problem when casting the value:

public void loadGrid(Sudoku testGrid) {
    try {
        FileInputStream fileIn = new FileInputStream(System.getProperty("user.home") + "\\tmp\\grid.grd");
        ObjectInputStream in = new ObjectInputStream(fileIn);
        testGrid.sudokuGrid = (Sudoku.sudokuGrid) in.readObject();
        in.close();
        fileIn.close();
    } catch(IOException i) {
        i.printStackTrace();
    } catch(ClassNotFoundException c) {
        c.printStackTrace();
    }
}

Sudoku is a class containing an ArrayList of ArrayList variable. I run into:

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
Sudoku.sudokuGrid cannot be resolved to a type

So, shouldn't the cast be to something like (List<ArrayList<?>>) in.readObject(); ? — Keppil
– Keppil, Commented Jan 4, 2015 at 15:19
Yes, what is sudokuGrid? a field in class Sudoku? casts are types, not variables. What are you trying to do? — Maurice Perry
– Maurice Perry, Commented Jan 4, 2015 at 15:21

Jean Logeart · Accepted Answer · 2015-01-04 15:22:17Z

3

You need to cast to the type of Sudoku.sudokuGrid, not the sudokuGrid field itself:

testGrid.sudokuGrid = (ArrayList<ArrayList<SomeType>>) in.readObject();

answered Jan 4, 2015 at 15:22

Jean Logeart

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