How to push/get data from Firebase and add to a bidimensional array using Java?

I already have TOPSIS algorithm that can calculate data from an array[][]. Now I’m going to use the data from:

dummy data:

double[][] data= {
                {887, 475, 4, 128, 186, 3621000},
                {887, 475, 8, 128, 189, 4011000},
                {1481, 991, 4, 128, 186, 4767000},
                {1481, 991, 8, 128, 186, 5157000},
                {1481, 991, 8, 256, 189, 5376000}};

to database’s data

dao_pc.get(key).addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                ArrayList<Item_pc> item_pcs = new ArrayList<>();
                for (DataSnapshot data : snapshot.getChildren()) {
                    Item_pc item_pc = data.getValue(Item_pc.class);
                    item_pcs.add(item_pc);
                    key = data.getKey();
                }
                adapter_pc = new Adapter_pc(getApplicationContext(), item_pcs);
                recyclerView.setAdapter(adapter_pc);
                adapter_pc.notifyDataSetChanged();
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {
            }
        });

My Item_pc.class

public class Item_pc {
    private String cpu;
    private String gpu;
    private String ram;
    private String ssd;
    private String power;
    private String harga;

    public Item_score(String cpu, String gpu, String ram, String ssd, String power, String harga) {
        this.cpu = cpu;
        this.gpu = gpu;
        this.ram = ram;
        this.ssd = ssd;
        this.power = power;
        this.harga = harga;
    }

    public Item_pc(){}

    public String getCpu() {return cpu;}
    public void setCpu(String cpu) {this.cpu = cpu;}
    public String getGpu() {return gpu;}
    public void setGpu(String gpu) {this.gpu = gpu;}
    public String getRam() {return ram;}
    public void setRam(String ram) {this.ram = ram;}
    public String getSsd() {return ssd;}
    public void setSsd(String ssd) {this.ssd = ssd;}
    public String getPower() {return power;}
    public void setPower(String power) {this.power = power;}
    public String getHarga() {return harga;}
    public void setHarga(String harga) {this.harga = harga;}

Condition:

1. I can get data from firebase using arraylist
2. I can calculate data using dummy array with TOPSIS algorithm

problem : how to calculate data from firebase with TOPSIS algorithm? I have trouble that data from firebase need to use Arraylist format, I don’t know how to store data on array[][] like array_push(PHP version) on java android.

Answer

First of all, do not store numbers as Strings in the database nor in your Item_pc class. If you have the values stored as Strings, change them to int, for example. So your class declaration should look like this:

class Item_pc {
    private int cpu;
    private int gpu;
    private int ram;
    private int ssd;
    private int power;
    private int harga;

    public Item_pc(int cpu, int gpu, int ram, int ssd, int power, int harga) {
        this.cpu = cpu;
        this.gpu = gpu;
        this.ram = ram;
        this.ssd = ssd;
        this.power = power;
        this.harga = harga;
    }

    public Item_pc() {
    }

    public int getCpu() {
        return cpu;
    }

    public void setCpu(int cpu) {
        this.cpu = cpu;
    }

    public int getGpu() {
        return gpu;
    }

    public void setGpu(int gpu) {
        this.gpu = gpu;
    }

    public int getRam() {
        return ram;
    }

    public void setRam(int ram) {
        this.ram = ram;
    }

    public int getSsd() {
        return ssd;
    }

    public void setSsd(int ssd) {
        this.ssd = ssd;
    }

    public int getPower() {
        return power;
    }

    public void setPower(int power) {
        this.power = power;
    }

    public int getHarga() {
        return harga;
    }

    public void setHarga(int harga) {
        this.harga = harga;
    }
}

Assuming that you get from the database a list that looks like this:

ArrayList<Item_pc> item_pcs = new ArrayList<>();
item_pcs.add(new Item_pc(887, 475, 4, 128, 186, 3621000));
item_pcs.add(new Item_pc(887, 475, 8, 128, 189, 4011000));
item_pcs.add(new Item_pc(1481, 991, 4, 128, 186, 4767000));
item_pcs.add(new Item_pc(1481, 991, 8, 128, 186, 5157000));
item_pcs.add(new Item_pc(1481, 991, 8, 256, 189, 5376000));

To create the two-dimensional array, please use the following lines of code:

int[][] data = new int[item_pcs.size()][6];
for (int i = 0; i < data.length; i ++) {
    Item_pc item_pc = item_pcs.get(i);
    data[i] = new int[]{
            item_pc.getCpu(),
            item_pc.getGpu(),
            item_pc.getRam(),
            item_pc.getSsd(),
            item_pc.getPower(),
            item_pc.getHarga()
    };
}
for (int[] d : data) {
    for (int i : d) {
        System.out.print(i + ", ");
    }
    System.out.println();
}

The result in the logcat will be:

887, 475, 4, 128, 186, 3621000, 
887, 475, 8, 128, 189, 4011000, 
1481, 991, 4, 128, 186, 4767000, 
1481, 991, 8, 128, 186, 5157000, 
1481, 991, 8, 256, 189, 5376000,