getProperty() always returns null - Java

Question

In the following code the getProperty() method always returns null, even if I add a default for

loadNumberOfAccounts();

so its not null, the next method which uses getProperty() will return null. storing the properties works flawlessly.

prop.get

also returns null.

public class AccountList {

    private static Properties prop = new Properties();
    private static final File DIRECTORY = Constants.DIRECTORY;
    private static final File BANK_ACCOUNTS_FILE = new 
    File(DIRECTORY.getName() + File.separator + "Accounts.txt");
    private static final FileOutputStream WRITER = assignWriter();
    private static final FileInputStream READER = assignReader();
    private static final List<Bank> ACCOUNT_LIST = new ArrayList<>();
    private static final String NUMBER_OF_ACCOUNTS = "NumberOfAccounts";
    private static final String BANK_ACCOUNT_NAME = "BankAccount";
    private static final String SEPERATOR = "-";
    private static int accounts = 0;
    static {
    BANK_ACCOUNTS_FILE.setReadOnly();
    }

    private static FileInputStream assignReader() {
        FileInputStream tmp = null;

        try {
            tmp = new FileInputStream(BANK_ACCOUNTS_FILE);
        } catch (FileNotFoundException e) {
            EvaluateErrors.eveluateException(e);
        }

        if (tmp == null) {
            EvaluateErrors.eveluateException(new NullPointerException());
        }

            return tmp;

    }

    private static FileOutputStream assignWriter() {
        BANK_ACCOUNTS_FILE.setWritable(true);
        FileOutputStream tmp = null;

        try {
            tmp = new FileOutputStream(BANK_ACCOUNTS_FILE);
        } catch (IOException e) {
            EvaluateErrors.eveluateException(e);
        }
        if (tmp == null) {
            EvaluateErrors.eveluateException(new NullPointerException());
        }

        BANK_ACCOUNTS_FILE.setReadOnly();
        return tmp;
    }

    public static void loadAccounts() {
        try {
                prop.load(READER);
        } catch (IOException e) {
            EvaluateErrors.eveluateException(e);
        }

        loadNumberOfAccounts();
        loadAccountsList();
        for (Bank object : ACCOUNT_LIST) { //to try and debug
            System.out.println(object.getName());
            System.out.println(object.getId());
            System.out.println(object.getBankAccountFunds());
            System.out.println(object.getOverdrawFee());

        }

    }

    public static void saveAccounts() {
        BANK_ACCOUNTS_FILE.setWritable(true);
        saveAccountsList();
        saveNumberOfAccounts();
        try {
                prop.store(WRITER, null);
        } catch (IOException e) {
            EvaluateErrors.eveluateException(e);
        } finally {
            CloseLogs();
            BANK_ACCOUNTS_FILE.setReadOnly();
        }
    private static void loadNumberOfAccounts() {

        String string = prop.getProperty(NUMBER_OF_ACCOUNTS);
        System.out.println(string); // always null
        try {
            accounts = Integer.parseInt(string);
        } catch (NumberFormatException e) { // this exception is thrown 
        // because string is always null. 
            EvaluateErrors.eveluateException(e);
        } 
// more methods ...

i'm sure the answer is quite simple and I have just missed it, but I have exhausted all options.

Accounts.txt looks like this

NumberOfAccounts=1
OtherStoredProperties=etc
etc...

UPDATE

I have found the bug but do not know why it's happening, nor how to fix it.

Turns out that if I change

private static final WRITER = assignWriter();

to

WRITER = null 

the getProperty() method works flawlessly. I obviously get a NullPointerException when attempting to store the property file because WRITER = null, however, that's an easy fix. What I don't understand is, why does assigning the WRITER cause the getProperty() method to only return null?

Answer 1

You can easily set and get the key value pairs for restricting the access. And it's safe when you push your code on remote git like github.

See the full code below:

1. Config.java class

   import java.io.*; import java.util.Properties;

   public class Config {

   Properties p;
   final String filename = "config.properties";
   
   public Config() throws FileNotFoundException {
   }
   
   //Storing environmental values
   public void setConfigValues() throws IOException {
       OutputStream os = new FileOutputStream(filename);
       p = new Properties();
       p.setProperty("name","Anand");
       p.setProperty("age","27");
       p.store(os, null);
   }
   
   //retrieving environmental values
   public String getConfigValues(String key) throws IOException {
       InputStream is = new FileInputStream(filename);
       p = new Properties();
       String name;
   
       p.load(is);
       name = p.getProperty(key);
       return name;
   }
   

   }

2. Main.java class

   import java.io.IOException;

   public class Main {
   
       public static String propertyValue;
   
       public static void main(String[] args) throws IOException {
   
           Config cfg = new Config();
           cfg.setConfigValues();
           propertyValue = cfg.getConfigValues("name");
           System.out.println(propertyValue);
           System.out.println(cfg.getConfigValues("age"));
       }
   
   }