Java - Very basic and simple bicycle Part's inventory database application.

BicyclePart.java

package com.masoomyf;




/**

 * com.masoomyf created by masoomyf on 28-01-2018.

 */

//Class for bicycle parts, its attributes.

public class BicyclePart {

    //For storing part number.

    public long id;

    //For storing part name.

    public String name;

    //For storing list price.

    public double listPrice;

    //For storing sale price.

    public double salePrice;

    //For storing onSale whether true or false.

    public boolean onSale;

    //For storing quantity.

    public int quantity;







    //Constructor.

    public BicyclePart(long id, String name, double listPrice, double sellPrice, boolean onSale,int quantity) {

        //Initialize of new Object Bicycle part

        //with the given value.

        this.id = id;

        this.name = name;

        this.listPrice = listPrice;

        this.salePrice = sellPrice;

        this.onSale = onSale;

        this.quantity = quantity;

    }




    //It will take string line like: akjs,1234567890,12.2,52.3,false,10 and

    //convert it to bicycle object by splitting it with comma

    //We use static here to call it directly without creating BicyclePart object.

    //and will crete new Bicycle part and return it.

    public static BicyclePart getPartFromString(String string){

        //split function split the string and give its array.

        //string example: akjs,1234567890,12.2,52.3,false,10

        //ajks stores in 0 index, 1234567890 stores in 1 index and so on after splitting.

        String[] parts = string.split(",");




        //Creating new object with the split array and return it.

        //Long.parseLong or Interger.parseInt or any other use to convert string object

        //in the appropriate data type.

        return new BicyclePart(Long.parseLong(parts[1]), parts[0],

                Double.parseDouble(parts[2]),Double.parseDouble(parts[3]),

                Boolean.parseBoolean(parts[4]),Integer.parseInt(parts[5]));

    }







    public String toString(){

        //just return all the attribute, with comma between them,

        //to save it in database txt file.

        return name + "," + id + "," + listPrice + "," + salePrice + "," + onSale;

    }




}

Main.java

package com.masoomyf;




import java.io.*;

import java.util.*;




public class Main {

    //To store all bicycle parts.

    private static ArrayList<BicyclePart> bicycleParts;

    //flag if changes is made in database or not.

    //if yes save it.

    private static boolean databaseUpdated = false;

    //main database file.

    private static File wareHouseFile;







    public static void main(String[] args) {

        //initialize new ArrayList.

        //Array list is use instead of array because it is expandable as

        //well as it will collapse after deleting object.

        bicycleParts = new ArrayList<>();

        //Creating File object of database file.

        wareHouseFile = new File("wareHouseDb.txt");

        //for reading user input.

        Scanner inputReader = new Scanner(System.in);

        //Now check database file exists or not.

        //If there is no Bicycle parts in database, or user run it first time

        //Its return false, because there will be no database file.

        if(wareHouseFile.exists()){

            // file is exists, try to read it.

            try {

                //reading main file.

                //Creating file input stream to read file. and passing File object

                //of database txt file.

                FileInputStream inputStream = new FileInputStream(wareHouseFile);

                //Creating buffered reader for file input stream.

                //It's allow to read file line by line and many more options.

                //but we need only to read line by line.

                BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));

                //Creating String line, for storing each line of database file.

                String line;

                //loop until there is no new line available in database file.

                //If there is no new line its return null and while loop breaks.

                while ((line=reader.readLine())!=null){

                    //check whether line is empty or not.

                    //if line is empty get next line.

                    if(line.isEmpty()){

                        continue;

                    }

                    //If line is not empty perform the following.

                    //get new line from file and add it to bicycle.

                    //create new bicycle part and add it to arrayList.

                    BicyclePart bicyclePart = BicyclePart.getPartFromString(line);

                    bicycleParts.add(bicyclePart);

                }




            }catch (Exception ignore){

                //If we get any error during reading file.

                //output error message.

                System.out.println("Cant read ware house database.");

            }

        }




        //Now display these option, until user write quit.

        while (true){

            //It will useful when user chooses an option another that quit,

            //It allow user to read the previous message of console.

            System.out.println("Press any key to continue.....");

            //It will not continue until user press any button and enter.

            inputReader.nextLine();

            //User pressed enter, it means user read the previous information.

            //Now display menu again(or first time).

            System.out.println("Please select your option from the following menu:");

            System.out.println("Read: Read an inventory delivery file");

            System.out.println("Enter: Enter a part");

            System.out.println("Sell: Sell a part");

            System.out.println("Display: Display a part");

            System.out.println("SortName: Sort parts by part name");

            System.out.println("SortNumber: Sort parts by part number");

            System.out.println("Quit:");




            System.out.print("Enter your choice: ");




            //Now read the choice of user.

            String choice = inputReader.nextLine();




            //According to choice call the appropriate option.

            if(choice.equalsIgnoreCase("read")){

                readFile(inputReader);

            }

            else if(choice.equalsIgnoreCase("enter")){

                enterPart(inputReader);

            }

            else if(choice.equalsIgnoreCase("sell")){

                sellPart(inputReader);

            }

            else if(choice.equalsIgnoreCase("display")){

                displayPart(inputReader);

            }

            else if(choice.equalsIgnoreCase("sortName")){

                sortByName();

            }

            else if(choice.equalsIgnoreCase("sortNumber")){

                sortByNumber();

            }

            else if(choice.equalsIgnoreCase("quit")){

                //If user select quit.

                //save the database and break the loop.

                saveDatabase();

                break;

            }




            else {

                //If user writes another option other than provided menu.

                //Give this error.

                System.out.println("Invalid option chosen.");

            }

        }




    }




    //Reading file inventory.txt.

    //Passing scanner here, so we don't need to create again a new scanner.

    private static void readFile(Scanner inputReader) {

        //prompt user to enter file name i.e. inventory.txt.

        System.out.println("Enter file name to read from: ");

        //read the fileName.

        String fileName = inputReader.nextLine();

        //Pass the filename to new File object.

        //It will allow to check whether file is exists or not.

        File file = new File(fileName);

        //If file not exists display error message and return from this method.

        if(!file.exists()){

            System.out.println("Error: File not exists.");

            return;

        }

        //If file exists try the following.

        try {

            //Create a new scanner by passing file object of inventory.txt

            //You can choose buffered reader also.

            //Just learn new thing.

            Scanner fileReader = new Scanner(file);

            //Marking this line as nextLine.

            //For future use.

            nextLine:

            //check if there is new line by looping.

            while (fileReader.hasNextLine()){

                //New line present, read the new line and store it into line.

                String line = fileReader.nextLine();

                //Now create a new Bicycle part.

                BicyclePart temp = BicyclePart.getPartFromString(line);

                //Now check, if this part exists in bicycleArrayList(database)

                //by comparing the temp part number with every bicycle part's number

                //store in array list(database)

                for (BicyclePart bicyclePart:bicycleParts){

                    //Check if bicycle part is present or not.

                    if(temp.id==bicyclePart.id){

                        //Yes present.

                        //Update it with new details, available in temp.

                        bicyclePart.listPrice = temp.listPrice;

                        bicyclePart.salePrice = temp.salePrice;

                        bicyclePart.onSale = temp.onSale;

                        //Add the quantity.

                        bicyclePart.quantity += temp.quantity;

                        //Flag the databaseUpdated to true.

                        //means save the database on exit, because it gets changed.

                        databaseUpdated = true;

                        //we use continue nextLine here because if we use only

                        //continue, for loop get's continue, and we don't it.

                        //so just skip the for loop and continue the while loop

                        //without executing the below lines.

                        //Below line is for new part's that are not available

                        //in our database.

                        continue nextLine;

                    }

                }

                //If there is no part that matches the temp, that's mean

                //part is new and add it to database.

                bicycleParts.add(temp);

                //Flag the databaseUpdated to true.

                //means save the database on exit, because it gets changed.

                databaseUpdated=true;

            }




        }catch (Exception e){

            //If something happen wrong, output the error.

            System.out.println("Error: " + e.getMessage());

        }




    }










    private static void enterPart(Scanner inputReader) {

        //Prompt and read all parts info from user.

        System.out.print("Enter part name: ");

        String name = inputReader.nextLine();




        //Below extra inputReader.nextLine is used because, we read a datatype

        //other than string.

        //If we don't call extra nextLine method, after reading this if we read a

        //string, it will give us a new line.

        //Example: we have to read an integer.

        //we use inputReader.nextInteger().

        //After that user write 45 or any number and press enter.

        //45 passed to caller, and enter remains in scanner, and we try to read new

        //line in future, it will just pass the enter which is in scanner.

        //rather than wait for a new string user will enter.

        System.out.print("Enter part number: ");

        long id = inputReader.nextLong();

        inputReader.nextLine();




        System.out.print("Enter list price: ");

        double listPrice = inputReader.nextDouble();

        inputReader.nextLine();







        System.out.print("Enter sell price: ");

        double salePrice = inputReader.nextDouble();

        inputReader.nextLine();







        System.out.print("Part is on sale? [true/false]: ");

        boolean onSale = inputReader.nextBoolean();

        inputReader.nextLine();







        System.out.println("Enter quantity: ");

        int quantity = inputReader.nextInt();

        inputReader.nextLine();







        //Now first check if bicycle part enter by user is present

        //in database or not. If yes update it and stop the method execution.

        for (BicyclePart bicyclePart: bicycleParts){

            if(bicyclePart.id == id){

                bicyclePart.listPrice = listPrice;

                bicyclePart.salePrice = salePrice;

                bicyclePart.onSale = onSale;

                bicyclePart.quantity += quantity;

                System.out.println("Bicycle part updated.");

                databaseUpdated = true;

                return;

            }

        }

        //If not add the new part to database.

        BicyclePart bicyclePart = new BicyclePart(id,name,listPrice,salePrice,onSale,quantity);

        bicycleParts.add(bicyclePart);

        System.out.println("New bicycle part is added.");

        databaseUpdated = true;

    }




    //For selling part.

    private static void sellPart(Scanner inputReader) {

        System.out.println("Enter part number: ");

        //Get the partNumber.

        long partNumber = inputReader.nextLong();

        //Remove the extra enter comes with long.

        inputReader.nextLine();

        //Check part enter by user is present in database or not.

        for (BicyclePart part: bicycleParts){

            if(partNumber == part.id){

                //if yes call sellPart(BicyclePart),

                //this method is also sellPart but with different signature

                //i.e. sellPart(Scanner).

                sellPart(part);

                //and stop executing this method.

                return;

            }

        }

        //If part is present then this line never execute.

        //If not present, this line will execute.

        //And show error message.

        System.out.println("Error: Bicycle part not exists.");

    }




    private static void sellPart(BicyclePart part){

        //check quantity is not less than one.

        //if yes give the error and stop execution of this method.

        if(part.quantity < 1){

            System.out.println("Error: No quantity left.");

            return;

        }

        //If quantity is more than zero(means available)

        //Print the part name and its cost.

        System.out.println("Part Name: " + part.name);

        // here tertiary operator is used for taking decision in line.

        // (true|false ? if true : if false)

        System.out.println("Part Cost: " + (part.onSale?part.salePrice:part.listPrice));

        if(part.onSale){

            System.out.println("Part is on sale.");

        }

        //Display the current date.

        System.out.println("Sold Time: " + new Date().toString());

        //decrease the part quantity.

        part.quantity--;

        //change the flag to true.

        //if it changes by another method, no problem.

        databaseUpdated=true;

    }




    //For displaying part.

    private static void displayPart(Scanner inputReader) {

        System.out.print("Enter part name: ");

        //read part name.

        //here no extra inputReader.nextLine() is use because string is read.

        //it automatically read the string with new line and omit it.

        String partName = inputReader.nextLine();

        //loop through database bicycle array list and check whether part name

        //is available or not.

        for (BicyclePart part: bicycleParts){

            if(partName.equalsIgnoreCase(part.name)){

                //if available call displayPart(BicyclePart) method.

                displayPart(part);

                //return.

                return;

            }

        }

        //if no part is available display the error.

        System.out.println("Error: Bicycle part not exists.");

    }




    //simple displayPart method.

    private static void displayPart(BicyclePart part) {

        System.out.println("Part Name: " + part.name);

        System.out.println("Part Cost: " + (part.onSale?part.salePrice:part.listPrice));

    }




    //sortByName method.

    private static void sortByName() {

            //sort the arraylist with the help of new Comparator.

        //java has compare option for datatype pre-defined in java,

        //If we create a new datatype(i.e. class), we have to implement and override the compare

        //method.

        bicycleParts.sort(new Comparator<BicyclePart>() {

            @Override

            public int compare(BicyclePart o1, BicyclePart o2) {

                //Compare the Bicycle Name with another one.

                //Java has string compare method.

                //so we use here and return the compare value to Comparator.

                return o1.name.compareToIgnoreCase(o2.name);

            }

        });

        //Now simply print all parts avail in database.

        System.out.println("Sorted part names: ");

        for (BicyclePart bicyclePart: bicycleParts){

            System.out.println(bicyclePart.name);

        }

    }




    //same as above but, here only change is that arraylist is sort by it's part number

    private static void sortByNumber() {

        bicycleParts.sort(new Comparator<BicyclePart>() {

            @Override

            //Compare with part number.

            public int compare(BicyclePart o1, BicyclePart o2) {

                return Long.compare(o1.id,o2.id);

            }

        });

        //Print the sorted arrayList.

        System.out.println("Sorted part names: ");

        for (BicyclePart bicyclePart: bicycleParts){

            System.out.println(bicyclePart.name);

        }

    }




    private static void saveDatabase() {

        //Check databaseUpdated flag.

        //If it is false, means no method execute which change the current database.

        //Therefore no need to save it.

        //return back.

        if(!databaseUpdated)return;




        //if it is true. write it to file.

        //first write it to temp file.

        //then delete the old database file.

        //after that rename the temp file to database file.

        try {

            //Create file output stream to write the data.

            FileOutputStream outputStream = new FileOutputStream("temp.txt");

            //create buffered writer to write line by line.

            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(outputStream));

            //loop through all part available in array list(database)

            for (BicyclePart bicyclePart:bicycleParts){

                //write the bicycle part to file follow with a new line.

                //bicycle.toString is defined in BicyclePart.java

                //which gives whole thing in string with comma seperator.

                writer.write(bicyclePart.toString() + "\n");

            }

            //close the writer.

            writer.close();

            //close output stream.

            outputStream.close();

            //check if the old database file actually exists or not.

            //if exists delete it.

            if(wareHouseFile.exists())

                wareHouseFile.delete();

            //create a file object with name temp.txt

            File file = new File("temp.txt");

            //rename it to database file.

            file.renameTo(wareHouseFile);




        }catch (Exception ignore){

            //rise error if anything happens wrong.

            ignore.printStackTrace();




        }

    }

}