CODEWITHSUNDEEP
javaandroidperformancesqliteserialization
Ray Foss
Ray Foss

Reputation: 3883

Multi-dimensional Array to a string (for android's SQLite)

Java serialization of multidimensional array

Is there anyway to serialize a 2D array to a string, in memory?

I'm trying to serialize a 2D array to an SQLite3 string, so I can put it in a field. The problem with the example above is that the author used fileIO, which on mobile devices is a speed killer.

Upvotes: 1

Views: 2582

Answers (2)

pawelzieba
pawelzieba

Reputation: 16082

This code serialize int arrays of different sizes into String and deserialize it back into int arrays

private static final char NEXT_ITEM = ' ';

public static void main(String[] args) throws IOException {
    int[][] twoD    = new int[][] { new int[] { 1, 2, 2, 4, 4 }, new int[] { 3, 4, 0 }, new int[] { 9 } };

    int[][] newTwoD = null; // will deserialize to this

    System.out.println("Before serialization");

    for(int[] arr : twoD) {
        for(int val : arr) {
            System.out.println(val);
        }
    }

    String str = serialize(twoD);

    System.out.println("Serialized: [" + str + "]");

    newTwoD = deserialize(str);

    System.out.println("After serialization");

    for(int[] arr : newTwoD) {
        for(int val : arr) {
            System.out.println(val);
        }
    }
}

private static String serialize(int[][] array) {
    StringBuilder s = new StringBuilder();
    s.append(array.length).append(NEXT_ITEM);

    for(int[] row : array) {
        s.append(row.length).append(NEXT_ITEM);

        for(int item : row) {
            s.append(String.valueOf(item)).append(NEXT_ITEM);
        }
    }

    return s.toString();
}

private static int[][] deserialize(String str) throws IOException {
    StreamTokenizer tok = new StreamTokenizer(new StringReader(str));
    tok.resetSyntax();
    tok.wordChars('0', '9');
    tok.whitespaceChars(NEXT_ITEM, NEXT_ITEM);
    tok.parseNumbers();

    tok.nextToken();

    int     rows = (int) tok.nval;
    int[][] out  = new int[rows][];

    for(int i = 0; i < rows; i++) {
        tok.nextToken();

        int   length = (int) tok.nval;
        int[] row    = new int[length];
        out[i]       = row;

        for(int j = 0; j < length; j++) {
            tok.nextToken();
            row[j] = (int) tok.nval;
        }
    }

    return out;
}

Upvotes: 2

Judah Sali
Judah Sali

Reputation: 1098

User T3hC13h has an interesting approach here: http://www.dreamincode.net/forums/topic/100732-serializingdeserializing-a-2-dimensional-array/

Upvotes: 1

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