Thread: Variables equaling null in some class's but not others

I'm working on a programming and its loading strings from a file and settings variables equal to them. It's weird because in some class's they value of these variables is equal to what I am expecting, lets say "hello world" but in other class's they equal null. It makes no sense to me.

Heres the class thats reading the file

package encrypter;
 
import java.io.*;
import java.util.Scanner;
import java.security.SecureRandom;
import java.math.BigInteger;
 
public class Config {
 
	public String  name, passwordLogPath, randKeyPath;
 
	private Scanner getInput;
	private BufferedWriter out;
	private BufferedReader in;
	private String line = null;
	private SecureRandom random = new SecureRandom();
	public File configFile = new File(System.getProperty("user.home") + "/.encrypter/EConfig.conf"), 
			passwordLog,
			randKey;
 
	public void createRandomKey() throws IOException {
		randKey.createNewFile();
		out = new BufferedWriter(new FileWriter(randKey, true));
		out.write("Key: " + new BigInteger(130, random));
		out.newLine();
		out.close();
		loadConfig();
	}
 
	public void createConfig() throws IOException {
		System.out.println("Setup is begining...");
		new File(System.getProperty("user.home") + "/.encrypter").mkdir();
		configFile.createNewFile();
		out = new BufferedWriter(new FileWriter(configFile, true));
		System.out.print("Please enter your first name: ");
		getInput = new Scanner(System.in);
		name = getInput.nextLine();
		if (!name.equals(""))
			out.write("Name: " + name);
		else
			out.write("Name: Bob");
		out.newLine();
		System.out.print("ADVANCED: Path to password log (Leave blank for default): ");
		passwordLogPath = getInput.nextLine();
		if (!passwordLogPath.equals(""))
			out.write("Password_Log_Path: " + passwordLogPath);
		else
			out.write("Password_Log_Path: " + System.getProperty("user.home") + "/.encrypter/");
		out.newLine();
		System.out.print("ADVANCED: Path to randomly generated key (Leave blank for default): ");
		randKeyPath = getInput.nextLine();
		if (!randKeyPath.equals(""))
			out.write("Random_Key_Path: " + randKeyPath);
		else
			out.write("Random_Key_Path: " + System.getProperty("user.home") + "/.encrypter/");
		out.newLine();
		out.close();
		System.out.println("Setup is complete!");
		loadConfig();
	}
 
	public void loadConfig() throws IOException {
		Main m = new Main();
		if (configFile.isFile()) {
			in = new BufferedReader(new FileReader(configFile));
			//System.out.println("\tLoading configurations...");
			while ((line = in.readLine()) != null) {
				if (line.startsWith("Name: "))
					name = line.substring(6);
				if (line.startsWith("Password_Log_Path: "))
					passwordLogPath = line.substring(19);
				if (line.startsWith("Random_Key_Path: "))
					randKeyPath = line.substring(17);
			}
			passwordLog = new File(passwordLogPath + "encrypted.log");
			m.manage.data = passwordLog;
			if (!passwordLog.isFile())
				passwordLog.createNewFile();
			randKey = new File(randKeyPath + "Frozen_Vault.key");
			if (randKey.isFile()) {
				in = new BufferedReader(new FileReader(randKey));
				while ((line = in.readLine()) != null) {
					if (line.startsWith("Key: "))
						m.computerKey = line.substring(5);
				}
			} else {
				try {
					createRandomKey();
				} catch (IOException e) {e.printStackTrace(); }
			}
			//System.out.println("\tConfiguration Loaded!");
			//System.out.println(m.computerKey);
		} else {
			try {
				createConfig();
			} catch (IOException e) { e.printStackTrace(); }
		}
	}
}

This is the main class, also it is getting the proper value

package encrypter;
 
/**
 * 
 * @author Josh
 * @date Tuesday January 3, 2012 1:17 AM
 * If you modify this and release it please give me credit! Thank you.
 */
 
import java.io.IOException;
import java.util.*;
 
public class Main {
 
	public Scanner type; // Creates a scanner object.
	public String userKey, computerKey, password, verify; // Strings that will hold values.
	public String[] commands = {"help", "commands", "new", "ls", "rm / remove", "clear", "backup",
			"restore", "exit"}; // Array of commands
	public String[] descrip = {" - Displays helpful information."," - Lists current commands.",
			" - Alows you to save new passwords.", " - Lists currently saved passwords.", 
			" - Alows you to remove a single password.", " - Deletes all saved passwords.", 
			" - Backs up all your passwords.", " - Restores passwords from backup file.",
			" - Saves your work and exits the program."}; // Array of command Descriptions
 
	public Encrypt encrypt = new Encrypt(); // Creates object for the class "Encrypt".
	public Decrypt decrypt = new Decrypt(); // Creates object for the class "Decrypt".
	public FileManager manage = new FileManager();
	public Config conf = new Config();
	public static Commands c = new Commands();
 
	public static void main(String[] args) { // Main method, just fires up the program and loops through it.
		Main m = new Main();
		System.out.println("Frozen Vault Password Encrypter - Newbi3");
		try {
			m.conf.loadConfig();
		} catch (IOException e) { System.out.println("Error Loading Configuration File."); }
		System.out.println("\n\t Type 'help' for help...");
		m.type = new Scanner(System.in);
		System.out.println(m.conf.passwordLogPath);
		while (true) {
			System.out.print("\n"+ m.conf.name + ", enter a command: ");
			c.switchCommand(m.type.nextLine());
			System.out.println(m.conf.passwordLogPath);
		}
	}
}

These are the rest of the class's returning nulls

package encrypter;
 
import java.io.*;
 
public class FileManager {
 
	public File data;
 
	public void removePassword(String lineToRemove) {
		Config conf = new Config();
		try {
			data = conf.passwordLog;
      		if (!data.isFile()) {
				System.out.println("\tF4 error - File not found.");
				return;
			}
 
			//Construct the new file that will later be renamed to the original filename. 
			File tempFile = new File(data.getAbsolutePath() + ".tmp");
 
			BufferedReader br = new BufferedReader(new FileReader(data));
			PrintWriter pw = new PrintWriter(new FileWriter(tempFile));
 
			String line = null;
 
			//Read from the original file and write to the new 
			//unless content matches data to be removed.
			while ((line = br.readLine()) != null) {        
				if (!line.trim().equals(lineToRemove)) {
					pw.println(line);
					pw.flush();
				}
			}
			pw.close();
			br.close();      
			//Delete the original file
			if (!data.delete()) {
				System.out.println("\tF4 error - Complications removing password.");
				return;
			}       
			//Rename the new file to the filename the original file had.
			if (!tempFile.renameTo(data)) {
				System.out.println("\tF5 error - Complications removing password."); 
			}
			System.out.println("\tPassword removed successfully!");
		} catch (FileNotFoundException ex) { ex.printStackTrace(); }
		catch (IOException ex) { ex.printStackTrace(); }
	}
 
	public void backupPasswords() throws IOException {
		Config conf = new Config();
		//data = new File(System.getProperty("user.home") + "/.encrypter/encrypted.log");
		data = conf.passwordLog;
      	if (!data.isFile()) {
			System.out.println("\tF4 error - File not found.");
			return;
		}
 
		//Construct the new file that will later be renamed to the original filename. 
		File backupFile = new File(data.getAbsolutePath() + ".backup");
 
		BufferedReader br = new BufferedReader(new FileReader(data));
		PrintWriter pw = new PrintWriter(new FileWriter(backupFile));
 
		String line = null;
 
		//Read from the original file and write to the new 
		while ((line = br.readLine()) != null) {
			pw.println(line);
			pw.flush();
		}
		pw.close();
		br.close();      
		System.out.println("\tPasswords backed up successfuly!");
	}
 
	public void loadBackup() throws IOException {
		Config conf = new Config();
		data = conf.passwordLog;
		//data = new File(System.getProperty("user.home") + "/.encrypter/encrypted.log");
      	if (!data.isFile()) {
			System.out.println("\tF4 error - File not found.");
			return;
		}
      	data.delete();
      	data.createNewFile();
		File backupFile = new File(data.getAbsolutePath() + ".backup");
		BufferedReader br = new BufferedReader(new FileReader(backupFile));
		PrintWriter pw = new PrintWriter(new FileWriter(data));
		String line = null;
		while ((line = br.readLine()) != null) {
			pw.println(line);
			pw.flush();
		}
		pw.close();
		br.close();      
		System.out.println("\tBackup file loaded successfuly!");
	}
 
	public void clearFile() throws IOException {
		data = new File(System.getProperty("user.home") + "/.encrypter/encrypted.log");
		data.delete();
		data.createNewFile();
		System.out.println("\tPasswords ereased successfuly!");
	}
 
}

package encrypter;
 
import java.io.IOException;
import java.util.Scanner;
 
public class Commands {
 
	public Scanner getInput;
	private Main m = new Main();
	private String choice;
 
	public void switchCommand(String cmd) {
		getInput = new Scanner(System.in);
		String c = cmd.toLowerCase();
		System.out.println(m.conf.passwordLogPath);
			switch(c) {
 
				case "help":
					System.out.println("\tJosh's Password Encrypter");
					System.out.println("\n\tWhat is a user key? The 'password' required to retrive your saved passwords");
					System.out.println("\tType 'commands' to see is a list of commands");
				break;
 
				case "commands":
					//System.out.println("\n");
					for (int i = 0; i < m.commands.length; i++)
						System.out.println("\t" + m.commands[i] + m.descrip[i]);
				break;
 
				case "new":
					System.out.print("Please enter your user key: ");
					m.userKey = getInput.nextLine();
					System.out.print("Please verify your user key: ");
					m.verify = getInput.nextLine();
					if (!m.userKey.equals(m.verify)) {
						System.out.println("\tYour user keys did not match!");
						m.verify = "";
					} else {
						System.out.print("Please enter your password to add: ");
						m.password = getInput.nextLine();
						System.out.print("Please verify your password to add: ");
						m.verify = getInput.nextLine();
						if (!m.password.equals(m.verify))
							System.out.println("\tPasswords did not match!");
						else {
							try {
								m.encrypt.write(m.userKey, m.password);
							} catch (Exception e) {
								System.out.println("\tE1 Error - File not found");
								System.out.println(m.manage.data);
							}
						}
					}
					m.verify = "";
					m.userKey = "";
					m.password = "";
				break;
 
				case "rm":
				case "remove":
					System.out.print("Please enter your user key: ");
					m.userKey = getInput.nextLine();
					System.out.print("Please verify your user key: ");
					m.verify = getInput.nextLine();
					if (!m.userKey.equals(m.verify)) {
						System.out.println("\tYour user keys did not match!");
					} else {
						System.out.print("Please enter the password to remove: ");
						m.password = getInput.nextLine();
						System.out.print("Please very the password to remove: ");
						m.verify = getInput.nextLine();
						if (!m.password.equals(m.verify)) {
							System.out.println("\tPasswords did not match, nothing removed.");
							m.verify = "";
						} else {
							String toRemove = m.encrypt.encrypted(m.userKey, m.password);
							m.manage.removePassword(toRemove);;
						}
					}
					m.verify = "";
					m.userKey = "";
					m.password = "";
				break;
 
				case "ls":
					System.out.print("Please enter your user key: ");
					m.userKey = getInput.nextLine();
					try {
					m.decrypt.readPassword(m.userKey);
					} catch (Exception e) {
						System.out.println("\tD2 Error - File not found.");
					}
					m.userKey = "";
				break;
 
				case "clear":
					System.out.print("This will erase ALL passwords. Continue? (Y/n): ");
					choice = getInput.nextLine();
					if (choice.equalsIgnoreCase("y")) {
						try {
							m.manage.clearFile();
						} catch (IOException e) {
							System.out.println("\tF3 Error - Could not access file.");
						}
					} else {
						System.out.println("\tPasswords NOT ereased.");
					}
				break;
 
				case "backup":
					System.out.print("This will create a backup file of your passwords. Continue? (Y/n): ");
					choice = getInput.nextLine();
					if (choice.equalsIgnoreCase("y")) {
						try {
							m.manage.backupPasswords();
						} catch (IOException e) { e.printStackTrace(); }
					} else
						System.out.println("\tPasswords were NOT backed up!");
				break;
 
				case "restore":
					System.out.print("This will replace all your saved data with your last backup. Continue? (Y/n): ");
					choice = getInput.nextLine();
					if (choice.equalsIgnoreCase("y")) {
						try {
							m.manage.loadBackup();
						} catch (IOException e) { e.printStackTrace(); }
					} else
						System.out.println("\tBackup file was NOT loaded!");
				break;
				case "exit":
					System.out.print("Are you sure you want to exit? (Y/n): ");
					String choice = getInput.nextLine();
					if (choice.equalsIgnoreCase("y")) {
						System.out.println("\tNow exiting Joshs' Password Encrypter...");
						System.exit(0);
					} else
						System.out.println("\tProgram did NOT exit.");
				break;
			}
		}
	}

package encrypter;
 
import java.io.*;
import java.util.*;
 
public class Decrypt {
 
	private Scanner scan; // Declares Scanner
	private String cpassword; // Creates a string to hold a value
 
	/**
	 * Decryption Algorithm
	 * How its works:
	 * Works the same way as the encryption but instead of adding "power" and "position" it subtracts
	 */
 
	public String decrypted(String key, String toRead) {
		int power;
		char[] userKey = key.toCharArray();
		char[] password = toRead.toCharArray();
 
		for (int i = 0; i < userKey.length; i++) {
			for (int b = 0; b < password.length; b++) {
				power = userKey[i];
				int position = password[b];
				char c = (char) (position - power);
				password[b] = c;
			}
		}
		return String.valueOf(password);
	}
 
	public void readPassword(String key) throws FileNotFoundException { // Reads the encrypted string then outprints the decrypted string.
		scan = new Scanner(new File(System.getProperty("user.home") + "/.encrypter/encrypted.log"));
		System.out.println("Current Passwords: ");
		while (scan.hasNext()) {
			cpassword = scan.nextLine();
			cpassword.toCharArray();
			System.out.println("\t" + decrypted(key, cpassword));
		}
	}
}

package encrypter;
 
import java.io.*;
 
public class Encrypt {
 
	private BufferedWriter out;
 
	/**
	 * Encryption Algorithm
	 * How it works:
	 * Converts string "key" and string "toWrite" into an array of characters
	 * Converts the arrays to integers "power" and "position"
	 * Adds them together and then converts back to an array of different characters and then back to a string.
	 */
 
	public String encrypted(String key, String toWrite) {
		int power;
		char[] userKey = key.toCharArray();
		char[] password = toWrite.toCharArray();
 
		for (int i = 0; i < userKey.length; i++) {
			for (int b = 0; b < password.length; b++) {
				power = userKey[i];
				int position = password[b];
				char c = (char) (position + power);
				password[b] = c;
				System.out.println(power + " " + (password[b = c]));
			}
		}
		return String.valueOf(password);
	}
 
	public void write(String key, String password) throws IOException { // Writes the encrypted string to a file.
		Main m = new Main();
		out = new BufferedWriter(new FileWriter(m.manage.data, true));
		out.write(encrypted(key, password));
		out.newLine();
		out.close();
		System.out.println("Your password was saved successfuly! " + encrypted(key, password));
	}
}

Look at the variable passwordLogPath defined in Config and lets say it equals "/home/bob/" in the class Main it will equal "/home/bob/" but in every other class it equals null. I don't understand it's doing this.

When you create a new instance of Main, it is completely separate and distinct from any other Main objects that you've created. So you create a Main object in its main method and you fill its Config object's passwordLogPath variable with useful information. Then you create a completely separate Main object in the Commands class, and you should not expect that its Config object will hold the same information that was placed int he First Main object.

The bad solution is to use static variables. Just don't do this. A much better solution is to pass a valid reference of Main into Config and have Config use this reference rather than trying to create a new Main object in Config. So give the Commands class a setMain(Main main) method, call it and pass in the valid Main object, and you should be good to go.