CODEWITHSUNDEEP
javabinaryarraylistobjectoutputstreamobjectinputstream
JProg
JProg

Reputation: 189

Java - binary file I/O with array-list

I'm a beginner on java and I'm having problem using binary file input and output of an array list. I'm trying to store the data on the array list on a file and then use it to display it in the console. Here is some of my code, it runs but displays the wrong information and I'm also getting a warning. Any help on what is causing this problem? Thanks!

public class Towers {
    public static ArrayList<String> allMoves= new ArrayList<String>();
    static{
        allMoves.add( "These Are the Disk Moves:" );
    }

    public static void move(final int aNumDisks){
        move(aNumDisks, 1, 2, 3);
        String fileName = "solution.dat";
        try{
            ObjectOutputStream outputStream = 
                    new ObjectOutputStream(
                            new FileOutputStream (fileName));
            outputStream.writeObject(allMoves);
            outputStream.close( );
        }
        catch ( IOException e ){
            System.out.println("Error writing to file " + fileName);
            System.exit(0);
        }
    }

Display output file in the console.

public class TReporter {        
    public static void reportSol(){
        String fileName = "solution.dat";
        ArrayList<String> allMovesA = null;
        try{
            ObjectInputStream inputStream =
                    new ObjectInputStream(
                            new FileInputStream (fileName));
            allMovesA = (ArrayList<String>)inputStream.readObject(); //WARNING!
                           //Type safety: Unchecked cast from Object to ArrayList<String>
            inputStream.close();
        }
        catch (Exception e){
            System.out.println("Problem reading the file " + fileName);
            System.exit(0);
        }
        for (int i = 0; i < allMovesA.size(); ++i){
            System.out.println( allMovesA.get(i) );
        }

It should display something like this:

=== 0 disks move(int) ===
These Are the Disk Moves:

=== 0 disks move(,,) ===
These Are the Disk Moves:

=== 1 disk move(int) ===
These Are the Disk Moves:
Move disk from 1 to 3

=== 2 disks ===
These Are the Disk Moves:
Move disk from 1 to 2
Move disk from 1 to 3
Move disk from 2 to 3

=== 2 disks move(2,3,2,1) ===
These Are the Disk Moves:
Move disk from 3 to 2
Move disk from 3 to 1
Move disk from 2 to 1

=== 3 disks move(3) ===
These Are the Disk Moves:
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3

But im getting this:

=== 0 disks move(int) ===
These Are the Disk Moves:
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3

=== 0 disks move(,,) ===
These Are the Disk Moves:
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3

=== 1 disk move(int) ===
These Are the Disk Moves:
Move disk from 1 to 3

=== 2 disks ===
These Are the Disk Moves:
Move disk from 1 to 2
Move disk from 1 to 3
Move disk from 2 to 3

=== 2 disks move(2,3,2,1) ===
These Are the Disk Moves:
Move disk from 1 to 2
Move disk from 1 to 3
Move disk from 2 to 3

=== 3 disks move(3) ===
These Are the Disk Moves:
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3

Upvotes: 0

Views: 3247

Answers (1)

Martijn Courteaux
Martijn Courteaux

Reputation: 68907

The warning you get is completely normal. You can suppress it by inserting this line before the line with the warning:

@SuppressWarnings("unchecked")

And for the wrong info you got:

  • make sure you write the file before you try to read it, you might be using an old version of the file.
  • make sure that the ArrayList it does contain the right moves.

Upvotes: 2

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