SqliteHelper

package com.example.a07act;

import android.app.Activity;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteConstraintException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

import java.util.Arrays;
import java.util.LinkedList;

public class SqliteHelper  extends SQLiteOpenHelper {
    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "Activity.db";
    private static final String FLAVORS_CREATE = "CREATE TABLE IF NOT EXISTS Flavors (" +
            "ItemCode INTEGER," + // INTEGER = int
            "ItemDesc TEXT," +    // TEXT = varchar
            "Price REAL" +        // REAL = float/double
            ");";

    public SqliteHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(FLAVORS_CREATE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS Flavors");
        onCreate(db);
    }

    public static class Queries {
        Activity activity;
        SQLiteDatabase db;
        SqliteHelper sqliteHelper;
        public Queries(Activity activity) {
            this.activity = activity;
            sqliteHelper = new SqliteHelper(activity);
            db = sqliteHelper.getWritableDatabase();

            // Para lagi reset data kada restart
            db.execSQL("DROP TABLE IF EXISTS Flavors");
            db.execSQL(FLAVORS_CREATE);
        }


        public boolean populateData(ContentValues values) {
            return db.insert("Flavors", null, values) != -1;
        }

        public String[] retrieveItemCode() {
            String val = "";
            Cursor cursor = db.query(
                    "Flavors",
                    new String[] {"ItemCode"},
                    null,
                    null,
                    null,
                    null,
                    null
            );

            while(cursor.moveToNext()) {
                val += cursor.getInt(cursor.getColumnIndexOrThrow("ItemCode")) + ":";
            }

            return val.split(":");
        }

        public LinkedList<String> retrieveAllCol() {
            LinkedList<String> val = new LinkedList<>();
            Cursor cursor = db.query(
                    "Flavors",
                    new String[] {"ItemCode", "ItemDesc", "Price"},
                    null,
                    null,
                    null,
                    null,
                    null
            );

            while (cursor.moveToNext()) {
                String[] data = new String[3];
                data[0] = String.valueOf(cursor.getInt(cursor.getColumnIndexOrThrow("ItemCode")));
                data[1] = cursor.getString(cursor.getColumnIndexOrThrow("ItemDesc"));
                data[2] = String.valueOf(cursor.getDouble(cursor.getColumnIndexOrThrow("Price")));

                String join = Arrays.toString(data);
                val.add(join.substring(1, join.length()-1));
            }

            return val;
        }

        public LinkedList<String> retrieveAllCol(double price) {
            LinkedList<String> val = new LinkedList<>();
            Cursor cursor = db.query(
                    "Flavors",
                    new String[] {"ItemCode", "ItemDesc", "Price"},
                    "Price > ?",
                    new String[]{String.valueOf(price)},
                    null,
                    null,
                    null
            );

            while (cursor.moveToNext()) {
                String[] data = new String[3];
                data[0] = String.valueOf(cursor.getInt(cursor.getColumnIndexOrThrow("ItemCode")));
                data[1] = cursor.getString(cursor.getColumnIndexOrThrow("ItemDesc"));
                data[2] = String.valueOf(cursor.getDouble(cursor.getColumnIndexOrThrow("Price")));

                String join = Arrays.toString(data);
                val.add(join.substring(1, join.length()-1));
            }

            return val;
        }

        public boolean changePrice(int itemCode, double newPrice) {
            ContentValues values = new ContentValues();
            values.put("Price", newPrice);

            String selection = "ItemCode = ?";
            String[] selectionArgs = {String.valueOf(itemCode)};

            return db.update(
                    "Flavors",
                    values,
                    selection,
                    selectionArgs
            ) > 0;
        }
    }
}