Develop Reference

Why is the wait() and notify() not working in this program?

I have recently started working on this program, and I'm new to inter-thread communications such as wait and notify. However when I run this, the notify doesn't seem to execute correctly. Here is the code: (sorry about the extra stuff)
import java.util.Scanner;
public class Main {
public static void main(String[] args) throws InterruptedException {
Main console = new Main();
console.restart();
}
public void restart() throws InterruptedException {
Scanner restartinput = new Scanner(System.in);
System.out.println("System has been restarted");
System.out.println("Restarting requires an admin restart password.");
System.out.println("You may also login as a normal user to reboot but will cause that account to be temporarily locked.");
System.out.println("Enter 1 for normal user, 2 for admin");
String input12 = restartinput.nextLine();
boolean lockall = false;
if (input12.equals("1")) {
System.out.println("Enter username:");
String input13 = restartinput.nextLine();
if (input13.equals("normalusertest")) {
boolean passwordgotten2 = false;
while (passwordgotten2 == false) {
// Not perfect hash function, some Strings and numbers have the same hash.
int realhashedpassword2 = 1544190;
System.out.println("PIN:");
Scanner input = new Scanner(System.in);
String enteredpassword2 = input.nextLine();
String plaintextguess2 = new String(enteredpassword2);
if (plaintextguess2.hashCode() == realhashedpassword2) {
System.out.println("Access granted.");
passwordgotten2 = true;
} else if (plaintextguess2.equals("/override")) {
System.out.println("Admin override password:");
String overridepasswordguess2 = input.nextLine();
if (overridepasswordguess2.hashCode() == 843331265) {
System.out.println("Access granted.");
passwordgotten2 = true;
} else {
System.out.println("Access denied.");
System.exit(0);
}
} else {
System.out.println("Access denied. Incorrect password");
}
}
for (int w = 0; w <= 45; w++) {
System.out.println(".");
}
fulllogin(0, 1);
} else {
System.out.println("That is not a normal username");
}
}
if (input12.equals("2")) {
boolean gottenpassword3 = false;
while (gottenpassword3 == false) {
System.out.println("Enter the restart password:");
String input8 = restartinput.nextLine();
if (input8.hashCode() == 48818447) {
System.out.println("Access granted.");
System.out.println("Restarting.");
for (int j = 0; j <= 45; j++) {
System.out.println(".");
}
gottenpassword3 = true;
}
}
fulllogin(0, 0);
}
}
public void fulllogin(int lockall, int locknormalusertest) throws InterruptedException {
int lockall1 = lockall;
int locknormalusertest1 = locknormalusertest;
Scanner usernameScanner = new Scanner(System.in);
System.out.println("Username:");
String inputtedusername = usernameScanner.nextLine();
String username = login(inputtedusername, lockall1, locknormalusertest1);
int currentadministrativelevel = 0;
if (username.equals("admintest")) {
currentadministrativelevel = 2;
}
if (username.equals("normalusertest")) {
currentadministrativelevel = 1;
}
runCommands(username, currentadministrativelevel, lockall, locknormalusertest);
}
public void runCommands(String username, int administrativelevel, int lockall, int locknormalusertest) throws InterruptedException {
int currentadministrativelevel = administrativelevel;
System.out.println("Command:");
Scanner commandinput = new Scanner(System.in);
String input2 = commandinput.nextLine();
if (input2.equals("/manage")) {
if (currentadministrativelevel == 2) {
System.out.println("1 user to manage");
System.out.println("Enter 1 to manage normalusertest");
if (commandinput.nextLine().equals("1")) {
System.out.println("1 to view data, 2 to manage password, 3 to lock/unlock user");
String input1 = commandinput.nextLine();
if (input1.equals("1")) {
System.out.println("No data to view currently");
}
if (input1.equals("2")) {
System.out.println(
"To log in to this account use '/override' as the password. The admin override password is the square of the password for this account.");
}
if (input1.equals("3")) {
System.out.println("'/lock' or '/unlock'");
System.out.println("Command:");
String input10 = commandinput.nextLine();
if (input10.equals("/lock")) {
System.out.println("Reenter password to confirm lock:");
System.out.println("Reenter PIN:");
String input9 = commandinput.nextLine();
if (input9.hashCode() == 1662305) {
System.out.println("Locking normalusertest.");
for (int o = 0; o <= 45; o++) {
System.out.println(".");
}
fulllogin(lockall, 1);
}
}
if (input10.equals("/unlock")) {
System.out.println("Reenter password to confirm unlock:");
System.out.println("Reenter PIN:");
String input11 = commandinput.nextLine();
if (input11.hashCode() == 1662305) {
System.out.println("Unlocking normalusertest.");
for (int p = 0; p <= 45; p++) {
System.out.println(".");
}
fulllogin(lockall, 0);
}
}
}
}
}
if (currentadministrativelevel == 1) {
System.out.println("No users to manage.");
}
}
if (input2.equals("/chat")) {
System.out.println("'/view' or '/send'");
String input14 = commandinput.nextLine();
if (input14.equals("/send")) {
System.out.println("Enter a user to send a message to. Capitalization matters.");
String input15currenttouser = commandinput.nextLine();
System.out.println("Message:");
String input16currentmessage = commandinput.nextLine();
try {
sendMessage(username, input15currenttouser, input16currentmessage, lockall, locknormalusertest);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
if (input14.equals("/view")) {
synchronized (this) {
boolean viewed = true;
notifyAll();
Thread.sleep(15000);
}
}
}
if (input2.equals("/logout")) {
System.out.println("Logging out.");
;
for (int i = 0; i <= 45; i++) {
System.out.println(".");
}
fulllogin(lockall, locknormalusertest);
} else {
runCommands(username, currentadministrativelevel, lockall, locknormalusertest);
}
}
public String login(String username, int lockall, int locknormalusertest) throws InterruptedException {
if (username.equals("normalusertest") && (lockall == 1 || locknormalusertest == 1)) {
System.out.println("This account has been temporarily locked.");
fulllogin(lockall, locknormalusertest);
}
if (username.equals("normalusertest") && lockall == 0 && locknormalusertest == 0) {
boolean passwordgotten = false;
while (passwordgotten == false) {
// Not perfect hash function, some Strings and numbers have the same hash.
int realhashedpassword = 1544190;
System.out.println("PIN:");
Scanner input = new Scanner(System.in);
String enteredpassword = input.nextLine();
String plaintextguess = new String(enteredpassword);
if (plaintextguess.hashCode() == realhashedpassword) {
System.out.println("Access granted.");
passwordgotten = true;
} else if (plaintextguess.equals("/override")) {
System.out.println("Admin override password:");
String overridepasswordguess = input.nextLine();
if (overridepasswordguess.hashCode() == 843331265) {
System.out.println("Access granted.");
passwordgotten = true;
} else {
System.out.println("Access denied.");
System.exit(0);
}
} else {
System.out.println("Access denied. Incorrect password");
}
}
return "normalusertest";
}
if (username.equals("admintest")) {
boolean passwordgotten = false;
while (passwordgotten == false) {
// Not perfect hash function, some Strings and numbers have the same hash.
int realhashedpassword = 1662305;
System.out.println("PIN:");
Scanner input = new Scanner(System.in);
String enteredpassword = input.nextLine();
String plaintextguess = new String(enteredpassword);
if (plaintextguess.hashCode() == realhashedpassword) {
System.out.println("Access granted.");
passwordgotten = true;
} else {
System.out.println("Access denied. Incorrect password");
}
}
return "admintest";
} else {
System.out.println("Invalid username");
return "error";
}
}
public void sendMessage(String fromuser, String touser, String message, int lockall, int locknormalusertest) throws InterruptedException {
synchronized (this) {
fulllogin(lockall, locknormalusertest);
boolean viewed = false;
while (viewed == false) {
wait();
}
System.out.println("notify test");
}
}
}
After /view is typed, the program just waits and then has "Command:" again, even though it should be printing "notify test".

I didn't grasp the whole concept of the application, but two issues seem apparent:
You're not starting any threads, therefore, there won't be any
inter-thread communications, because the only thread you'll have is
Main. Running your application on multiple threads could be
achieved, for example, by having Main extend Thread, creating
multiple instances in your static main method, and calling
start() on each. (This is just a technical example that most
likely wouldn't be appropriate for your needs, as you wouldn't want
to start printing to the console from multiple threads.)
The following synchronized blocks are trying to communicate via a
boolean viewed, but since they're each creating it as their own
local variable, they never get to each other:
synchronized (this) {
fulllogin(lockall, locknormalusertest);
boolean viewed = false;
while (viewed == false) {
wait();
}
System.out.println("notify test");
}
// ...
synchronized (this) {
boolean viewed = true;
notifyAll();
Thread.sleep(15000);
}
Threads need to communicate via data that's scoped appropriately to be
accessible to all of them. For example, if you create the threads as in my
example in #1, you can create a static field on Main and all
instances will have access to that.
public class Main {
// The 'static' keyword makes this variable available to all Main instances
private static boolean viewed = false;
// ...
I'd suggest that you read up on Java scopes and dig into this excellent resource to get a better grasp on the concepts of multithreading: http://tutorials.jenkov.com/java-concurrency/index.html

Exception after using refractor - Java in Eclipse

I need to update my project, I used a lowercase on classes and its not standard coding convention. So, I have used the refractor > rename in eclipse for the classes. And now I get this exception/error:
Exception in thread "main" java.lang.NoClassDefFoundError:
FacebookClass/facebookClass (wrong name: FacebookClass/FacebookClass)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at java.io.ObjectInputStream.resolveClass(Unknown Source)
at java.io.ObjectInputStream.readNonProxyDesc(Unknown Source)
at java.io.ObjectInputStream.readClassDesc(Unknown Source)
at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.readObject(Unknown Source)
at FacebookClass.Driver.main(Driver.java:28)
I used the refractor and had the box checked to change all names, I don't know what the problem is.
Driver Class:
package FacebookClass;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Scanner;
public class Driver {
public static void main(String args[])
{
Scanner input = new Scanner(System.in);
String username;
String password;
int choice = 0;
FacebookClass facebook = new FacebookClass();
String filename = "save.ser";
// Deserializing facebook object
try
{
FileInputStream file = new FileInputStream(filename);
ObjectInputStream in = new ObjectInputStream(file);
facebook = (FacebookClass)in.readObject();
in.close();
file.close();
System.out.println("Succefully opened saved data.");
}
catch(IOException ex)
{
}
catch(ClassNotFoundException ex)
{
}
while (choice != 5)
{
choice = menu();
switch(choice)
{
case 1:
// List users
System.out.println("");
facebook.listUsers();
break;
case 2:
// Add a user
System.out.println("");
System.out.print("Enter a username: ");
username = input.nextLine();
facebook.addUser(username);
break;
case 3:
// Delete a user
System.out.print("Enter your username: ");
username = input.nextLine();
facebook.deleteUser(username);
break;
case 4:
// Get password hint
System.out.print("Enter your username: ");
username = input.nextLine();
facebook.getHint(username);
break;
case 5:
// Quit and serialize facebook object
try
{
FileOutputStream file = new FileOutputStream(filename);
ObjectOutputStream out = new ObjectOutputStream(file);
out.writeObject(facebook);
out.close();
file.close();
System.out.println("Data has been saved.");
}
catch(IOException ex)
{
}
}
}
}
public static int menu()
{
Scanner input = new Scanner(System.in);
int choice = 0;
System.out.println("");
System.out.println("1) List Users");
System.out.println("2) Add a User");
System.out.println("3) Delete a User");
System.out.println("4) Get Password Hint");
System.out.println("5) Quit");
System.out.print("Enter your choice: ");
choice = input.nextInt();
while (choice < 1 || choice > 5)
{
System.out.print("Try again: ");
choice = input.nextInt();
}
return choice;
}
}
FacebookClass Class:
package FacebookClass;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
public class FacebookClass implements Serializable
{
private ArrayList<FacebookUser> users = new ArrayList<FacebookUser>();
public void listUsers()
{
// Print user names of users array list
System.out.println("Users: ");
for (int i=0; i<users.size(); i++)
{
System.out.println((users.get(i)).getUsername());
}
}
public void addUser(String username)
{
Scanner input = new Scanner(System.in);
String password;
String hint;
// Add a user, check if name exists
Boolean nameCheck = false;
for (int i=0; i<users.size(); i++)
{
if (users.get(i).getUsername().equals(username))
{
nameCheck = true;
}
}
if (nameCheck)
{
System.out.println("Error! Username is already in
use.");
}
else
{
System.out.print("Enter a password: ");
password = input.nextLine();
System.out.print("Enter a password hint: ");
hint = input.nextLine();
FacebookUser user = new FacebookUser(username,
password);
user.setPasswordHint(hint);
users.add(user);
}
}
public void deleteUser(String username)
{
Scanner input = new Scanner(System.in);
String passwordTemp;
Boolean usernameCheck = false;
Boolean passwordCheck = false;
for (int i=0; i<users.size(); i++)
{
if ((users.get(i)).getUsername().equals(username))
{
System.out.print("Enter your password to
confirm: ");
passwordTemp = input.nextLine();
usernameCheck = true;
if
(!passwordTemp.equals(users.get(i).getPassword()))
{
System.out.println("Error! Passwords do
not match.");
usernameCheck = false;
passwordCheck = true;
}
if (!passwordCheck)
{
users.remove(i);
}
}
}
if (usernameCheck)
{
System.out.println("User has been succesfully
deleted.");
}
else if (!usernameCheck && !passwordCheck)
{
System.out.println("The entered username does not match
any users.");
}
}
public void getHint(String username)
{
Boolean nameCheck = false;
for(int i=0; i<users.size(); i++)
{
if (users.get(i).getUsername().equals(username))
{
users.get(i).getPasswordHelp();
nameCheck = true;
}
}
if (!nameCheck)
{
System.out.println("The entered username does not match
any users.");
}
}
}
FacebookUser Class:
package FacebookClass;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.*;
import java.lang.*;
import java.io.*;
public class FacebookUser extends UserAccount implements Cloneable,
Comparable<FacebookUser>, Serializable {
public FacebookUser(String username, String password) {
super(username, password);
}
private String passwordHint;
private ArrayList<FacebookUser> friends = new ArrayList<FacebookUser>
();
void setPasswordHint(String hint)
{
passwordHint = hint;
}
void friend(FacebookUser newFriend)
{
// Check if friend is in friends list. If not, add them
Boolean friendCheck = false;
for (int i = 0; i < friends.size(); i++)
{
if (friends.get(i) == newFriend)
{
friendCheck = true;
}
}
if (friendCheck)
{
System.out.println(newFriend.getUsername() + " is already are on " +
this.getUsername() + "'s friends list!");
}
else
{
friends.add(newFriend);
System.out.println(this.getUsername() +
"'s friend list: " + friends);
}
}
void defriend(FacebookUser formerFriend)
{
// Check if friend is in friends list. If they are, remove them
Boolean friendCheck = false;
for (int i = 0; i < friends.size(); i++)
{
if (friends.get(i) == formerFriend)
{
friendCheck = true;
}
}
if (!friendCheck)
{
System.out.println("They are not on friends list!");
}
else
{
friends.remove(formerFriend);
System.out.println(this.getUsername() + "'s friend
list: " + friends);
}
}
public Object clone() throws CloneNotSupportedException
{
return super.clone();
}
ArrayList<FacebookUser> getFriends()
{
// Create clone of face book users array list and return
ArrayList<FacebookUser> clone = (ArrayList) friends.clone();
return clone;
}
// Compare to method for sorting
#Override
public int compareTo(FacebookUser user) {
return
this.getUsername().compareToIgnoreCase(user.getUsername());
}
// Abstract get password help method
#Override
public void getPasswordHelp()
{
if (!(passwordHint == null))
{
System.out.println(this.getUsername() + "'s password
hint is: "+ passwordHint);
}
else
{
System.out.println(this.getUsername() + "'s password
hint has not been set");
};
}
}
UserAccount Class:
package FacebookClass;
import java.io.Serializable;
import FacebookClass.UserAccount;
public abstract class UserAccount implements Serializable
{
private String username = "";
private String password = "";
private Boolean active = false;
public abstract void getPasswordHelp();
public UserAccount(String username, String password) {
this.username = username;
this.password = password;
active = true;
}
public void createAccount(String username, String password)
{
this.username = username;
this.password = password;
active = true;
}
public boolean checkPassword(String password)
{
if (password.equals(this.password))
{
return true;
}
else
{
return false;
}
}
public void deactivateAccount()
{
active = false;
}
public String toString()
{
return (username);
}
public String getUsername()
{
return username;
}
public void setUsername(String username)
{
this.username = username;
}
public String getPassword()
{
return password;
}
public void setPassword(String password)
{
this.password = password;
}
public Boolean getActive() {
return active;
}
public void setActive(Boolean active) {
this.active = active;
}
#Override
public int hashCode()
{
final int prime = 31;
int result = 1;
result = prime * result + ((username == null) ? 0 :
username.hashCode());
return result;
}
#Override
public boolean equals(Object obj)
{
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
UserAccount other = (UserAccount) obj;
if (username == null)
{
if (other.username != null)
return false;
} else if (!username.equals(other.username))
return false;
return true;
}
}

Why am I getting "missing return statement" error in Java even though I have return statement and exception in thread main error in 2nd class?

For example, I am getting the error here- this is just a snippet. I got the error 3 times in 3 different operators.
public boolean delete(String name) {
for (int i = 0; i < directory.length; i++) {
if (directory[i].equalsIgnoreCase(name)) {
directory[i] = null;
return true;
}
else
return false;
}
}
I also have the same error here:
public boolean add(String name) {
if (directory.length == 1024)
return false;
for (int i = 0; i < directory.length; i++) {
if (directory[i].equalsIgnoreCase(name))
return false;
else
directory[directorySize++] = name;
return true;
}
}
And then in my second class (the user interface portion), I keep getting this error: Exception in thread "main" java.lang.NoClassDefFoundError: Directory
Here is the entire code for that class:
import java.io.*;
import java.util.*;
public class DirectoryWithObjectDesign {
public static void main(String[] args) throws IOException {
String directoryDataFile = "Directory.txt";
Directory d = new Directory(directoryDataFile);
Scanner stdin = new Scanner(System.in);
System.out.println("Directory Server is Ready!");
System.out.println("Format: command name");
System.out.println("Enter ^Z to end");
while (stdin.hasNext()) {
String command = stdin.next();
String name = stdin.next();
if (command.equalsIgnoreCase("find")) {
if (d.inDirectory(name))
System.out.println(name + " is in the directory");
else
System.out.println(name + " is NOT in the directory");
}
else if (command.equalsIgnoreCase("add")) {
if (d.add(name))
System.out.println(name + " added");
else
System.out.println(name + " cannot add! " + "no more space or already in directory");
}
else if (command.equalsIgnoreCase("delete")) {
if (d.delete(name))
System.out.println(name + " deleted");
else
System.out.println(name + " NOT in directory");
}
else {
System.out.println("bad command, try again");
}
}
}
}
And here is the code for my directory class:
import java.util.*;
import java.io.*;
public class Directory {
//public static void main(String[] args) {
final int maxDirectorySize = 1024;
String directory[] = new String[maxDirectorySize];
int directorySize = 0;
File directoryFile = null;
Scanner directoryDataIn = null;
public Directory(String directoryFileName) {
directoryFile = new File(directoryFileName);
try {
directoryDataIn = new Scanner(directoryFile);
}
catch (FileNotFoundException e) {
System.out.println("File is not found, exiting!" + directoryFileName);
System.exit(0);
}
while (directoryDataIn.hasNext()) {
directory[directorySize++] = directoryDataIn.nextLine();
}
}
public boolean inDirectory(String name) {
for (int i = 0; i < directory.length; i++) {
if (directory[i].equalsIgnoreCase(name))
return true;
else
return false;
}
}
public boolean add(String name) {
if (directory.length == 1024)
return false;
for (int i = 0; i < directory.length; i++) {
if (directory[i].equalsIgnoreCase(name))
return false;
else
directory[directorySize++] = name;
return true;
}
}
public boolean delete(String name) {
for (int i = 0; i < directory.length; i++) {
if (directory[i].equalsIgnoreCase(name)) {
directory[i] = null;
return true;
}
else
return false;
}
}
public void closeDirectory() {
directoryDataIn.close();
PrintStream directoryDataOut = null;
try {
directoryDataOut = new PrintStream(directoryFile);
}
catch (FileNotFoundException e) {
System.out.printf("File %s not found, exiting!", directoryFile);
System.exit(0);
}
String originalDirectory[] = {"Mike","Jim","Barry","Cristian","Vincent","Chengjun","susan","ng","serena"};
if (originalDirectory == directory)
System.exit(0);
else
for (int i = 0; i < directorySize; i++)
directoryDataOut.println(directory[i]);
directoryDataOut.close();
}
}

The point is that the compiler can't know if your for loop will be entered at all. Therefore you need a final return after the end of the for loop, too. In other words: any path that can possibly be taken within your method needs a final return statement. One easy way to achieve this ... is to have only one return statement; and put that on the last line of the method. This could look like:
Object getSomething() {
Object rv = null; // rv short for "returnValue"
for (int i=0; i < myArray.length; i++) {
if (whatever) {
rv = godKnowsWhat;
} else {
rv = IdontCare;
}
}
return rv;
}
In your second example, the indenting seems to indicate that you have a return in the else statement
directory[directorySize++] = name;
return true;
But when you look closer, you will realize that there are TWO statements after the else
else
directory[directorySize++] = name;
return true;
So this actually reads like
else
directory[directorySize++] = name;
return true;
Meaning: always put {braces} around all your blocks, even for (supposedly) one-liner then/else lines. That helps to avoid such mistakes, when a one-liner turns into a two-liner (or vice versa ;-)
The "NoClassDefFoundException" means: within the classpath that is specified to java ... there is no class Directory.class
To resolve that, you should study what the java classpath is about; and how to set it correctly.

Standard FTP Login java class

Is there a defined standard class for dealing with FTP login data? Something that already handles storing, sharing? Since I am relatively new to this, maybe someone else gave this topic already a thorough thinking. Could not find anything in Apache Commons so far...
For now I use my own class, it is not very fulfilling:
public class FTPLogin {
String hostaddress;
int port;
String name;
String password;
public FTPLogin() {
}
public FTPLogin(String hostaddress, int port, String name,
String password) {
this.hostaddress = hostaddress;
this.port = port;
this.name = name;
this.password = password;
}
#Override
public String toString() {
return hostaddress + ";" + port + ";" + name + ";" + password;
}
}

There is no Standard, I prefer ftp4j

import java.util.Scanner;
class users
{
String username;
String password;
String[][] accounts = {{"Karthik", "k123"},{"Ram", "r123"}};
users(String user, String pass)
{
username = user;
password = pass;
}
public boolean auth()
{
if((username == accounts[0][0]) && (password == accounts[0][1]))
{
return true;
}
else if((username == accounts[1][0]) && (password == accounts[1][1]))
{
return true;
}
else
{
return false;
}
}
public static void main(String[] args)
{
Scanner sc=new Scanner(System.in);
System.out.println("Enter name:");
String s=sc.next();
System.out.println("Enter pid:");
int i=sc.nextInt();
users obj=new users(s,i);
System.out.println(obj.auth());
}
}

import java.util.Hashtable;
import java.util.Scanner;
class Login
{
public boolean checkValue(String name,String Password)
{
Hashtable<String,String> map=new Hashtable<String,String>();
map.put(name,Password);
//System.out.println(map);
if(name.equals("abcd") && Password.equals("1234"))
{
return true;
}
else if(name.equals("Mnop") && Password.equals("5678"))
{
return true;
}
else if(name.equals("xyzx") && Password.equals("7890"))
{
return true;
}
else
{
return false;
}
}
public static void main(String[] args)
{
Scanner sc=new Scanner(System.in);
System.out.println("Enter a name s:");
String s=sc.next();
System.out.println("Enter a password p:");
String p=sc.next();
Login obj=new Login();
boolean status=obj.checkValue(s,p);
System.out.println(status);
}
}

DeSerialized Object containing ArrayList has all null values

Hopefully someone can provide some insight on this issue. I have created an instance of an object that contains an ArrayList of information (username, password, password hint). I am trying to serialize the object. It looks like it is serializing properly, but when I restart the project to deserialize, it returns null values in the ArrayList. Why is it returning null values for the ArrayList objects?
Driver Class:
import java.io.Serializable;
public class TestingDriver implements Serializable{
private static final long serialVersionUID = 12345L;
private static TestingAccount users = new TestingAccount();
public static void main(String[] args) {
int foreverLoop = 0;
users = DeSerialize.main();
while (foreverLoop < 1) {
int selection = users.displayMainMenu();
if (selection == 1) {
users.listUsers();
}
else if (selection == 2) {
users.addUser();
}
else if (selection == 3) {
users.deleteUser();
}
else if (selection == 4) {
users.getPasswordHint();
}
else if (selection == 5) {
Serialize.main(users);
System.exit(0);
}
else {
System.out.println("That option does not exist. Please try again.");
}
}
}
}
TestingUser Class (objects of this class will populate the ArrayList):
import java.io.Serializable;
public class TestingUser extends UserAccount implements Serializable, Comparable <TestingUser> {
private static final long serialVersionUID = 12345L;
public TestingUser(String username, String password, String passwordHint) {
super(username, password, passwordHint);
}
public TestingUser() {
}
#Override
public void getPasswordHelp() {
System.out.println("");
System.out.println("Password hint: " + passwordHint);
System.out.println("");
}
#Override
public int compareTo(TestingUser otherAccount) {
if (this.username.compareToIgnoreCase(otherAccount.username) < 0) {
return -1;
}
else if (this.username.compareToIgnoreCase(otherAccount.username) > 0) {
return 1;
}
else {
return 0;
}
}
}
TestingAccount class (calling this class creates an object that contains the ArrayList):
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Scanner;
public class TestingAccount implements Serializable {
private static final long serialVersionUID = 12345L;
public ArrayList<TestingUser> userList;
private String username;
private String password;
private String passwordHint;
public TestingAccount() {
userList = new ArrayList<TestingUser>();
}
public void listUsers() {
for (int i=0; i<this.userList.size(); i++) {
System.out.println(this.userList.get(i));
}
}
#SuppressWarnings("resource")
public void addUser() {
Scanner input = new Scanner(System.in);
System.out.println("Please enter a username: ");
username = input.next();
TestingUser tempAccount = new TestingUser(username, null, null);
if (this.userList.contains(tempAccount) == true) {
System.out.println("This user already exists.");
}
else {
System.out.println("Please enter a password: ");
password = input.next();
System.out.println("Please enter a password hint: ");
passwordHint = input.next();
tempAccount.password = password;
tempAccount.passwordHint = passwordHint;
this.userList.add(tempAccount);
System.out.println("Account " + tempAccount.username + " has been added.");
}
}
#SuppressWarnings("resource")
public void deleteUser() {
Scanner input = new Scanner(System.in);
System.out.println("Please enter the username to be deleted: ");
username = input.next();
TestingUser tempAccount = new TestingUser(username, null, null);
if (this.userList.contains(tempAccount) == true) {
int actIndex = this.userList.indexOf(tempAccount);
System.out.println("Please enter the password: ");
password = input.next();
tempAccount.password = password;
boolean passwordGood = this.userList.get(actIndex).CheckPassword(tempAccount);
int accountIndex = this.userList.indexOf(tempAccount);
tempAccount = this.userList.get(accountIndex);
if (passwordGood == true) {
this.userList.remove(actIndex);
System.out.println("The account has been deleted.");
}
else {
System.out.println("The password is not correct.");
}
}
else {
System.out.println("The account does not exist.");
}
}
#SuppressWarnings("resource")
public void getPasswordHint() {
Scanner input = new Scanner(System.in);
System.out.println("Please enter a username: ");
username = input.next();
TestingUser tempAccount = new TestingUser(username, null, null);
if (this.userList.contains(tempAccount) == true) {
int actIndex = this.userList.indexOf(tempAccount);
tempAccount = this.userList.get(actIndex);
System.out.println("The password hint isL: " + tempAccount.passwordHint);
}
else {
System.out.println("The account does not exist.");
}
}
#SuppressWarnings({ "resource" })
public int displayMainMenu() {
int selection = 0;
Scanner input = new Scanner(System.in);
System.out.println("");
System.out.println("System Menu:");
System.out.println("1. List Users");
System.out.println("2. Add User");
System.out.println("3. Delete User");
System.out.println("4. Get Password Hint");
System.out.println("5. Quit");
System.out.println("");
System.out.println("What would you like to do?");
selection = input.nextInt();
return selection;
}
}
Serialize class:
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
public class Serialize {
public static void main(TestingAccount users) {
try {
ObjectOutputStream oos = new ObjectOutputStream(
new FileOutputStream("serialize"));
oos.writeObject(users);
oos.close();
} catch (FileNotFoundException e1) {
System.err.println("File not found.");
} catch (IOException e2) {
System.err.println("Unable to serialize.");
e2.printStackTrace();
}
}
}
Deserialize class:
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.ObjectInputStream;
public class DeSerialize {
public static TestingAccount main() {
TestingAccount deSerialize = null;
try {
ObjectInputStream ois = new ObjectInputStream(
new FileInputStream("serialize"));
deSerialize = (TestingAccount) ois.readObject();
ois.close();
} catch (FileNotFoundException e1) {
System.err.println("Unable to open file.");
} catch (IOException e2) {
System.err.println("Could not de-serialize.");
e2.printStackTrace();
} catch (ClassNotFoundException e3) {
System.err.println("Could not cast to class TestingAccount.");
}
return deSerialize;
}
}

It looks like UserAccount isn'tSerializable. So when you serialize the derived TestingUser class, none of the UserAccount data gets serialized. See Object Serialization Specification #2.1.13(a). TestingUser doesn't have any instance state of its own to serialize.
The solution is to make UserAccount implement Serializable.
Not sure why this comes as a surprise.