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Continue the program execution in multiple try-catch statements scenario after catching exception

I have the following code running in my project:
HashMap<String, DeviceData> deviceMap = getAllDevices();
int status = 0;
DeviceHandle devHandle = null;
for (LicenseData licenseData:listLicenses) {
Map<String, String> licenseMap = licenseData.getLicenseKeyValues();
if ((licenseMap != null && !licenseMap.isEmpty())) {
String keyDecrypt = licenseMap.get("key");
Date expiryDate = new Date(Long.parseLong(licenseMap.get("expiryDate")));
boolean allowForeign = Boolean.parseBoolean(licenseMap.get("allowForeign"));
String ipDecrypt = licenseMap.get("ipAddress");
if (expiryDate.compareTo(new Date()) > 0 || keyDecrypt.equals(licenseData.getKey().getCurrentValueAsString()))
{
try {
DeviceData device = deviceMap.get(ipDecrypt);
devHandle = (DeviceHandle)device.getHandle();
if(device != null && devHandle != null) {
deviceMap.remove(ipDecrypt, device);
System.out.println("After deletion device map.");
System.out.println(deviceMap);
createUser(devHandle);
try {
if (allowForeign) {
Process pr = Runtime.getRuntime().exec(SomeOperation);
status = pr.waitFor();
if (status == 0)
//Debug Statement
else
//Error Debug Statemnt
deleteUser(devHandle);
}
else {
Process pr = Runtime.getRuntime().exec(SomeOperation);
status = pr.waitFor();
if (status == 0)
//Debug Statement
else
//Error Debug Statement
deleteUser(devHandle);
}
} catch(Exception e) {
//Exception statement
deleteUser(devHandle);
}
} catch(Exception e) {
e.printStackTrace();
}
}
}
}
Explanation: I have a list of licenses for my application in listLicenses. All the devices present in the server are in deviceMap. For each license, I am decrypting it and getting the values. If license for a device is present, I get a handle on that device and doing some operations.
The issue is:
If I am not able to get a handle on device(getHandle()), or if I am not able to create a user after getting the device handle(createUser()), an exception is thrown. These methods are very hierarchical, i.e I am calling them from here, they are in another class throwing own exceptions and for their operation, they call other methods.
If there are three devices in the map, and three licenses, and if for the first one I am not able to get a handle or create a user, device is removed from deviceMap but no further execution happens i.e. for the next two devices.
If exception occurs for on device, I want to continue the exception for other two devices. I tried using return but couldn't get it to work.
Please help.Also, please forgive for the syntax and if any mismatch is there in the code.

Make use of first try's catch block.
This is how I handled when I faced same kind of situation.
catch (Exception exp) {
if (exp instanceof NullPointerException) {
log.info"Invalid/ Inactive ");
} else if (exp instanceof NonUniqueResultException) {
log.info("Multiple records existed");
} else {
exp.printStackTrace();
errorMsgs.append("Unexpected Error Occured. Please contact Admin.");
}
}

Password Masking in Java with Scanner

I'm a high school student learning Java and I want to know how to change input text automatically into an asterisk in Scanner. This is for a simple log-in system I have made for a project. My code is
Scanner scan = new Scanner(System.in);
boolean correctLogin = false;
String username;
String password;
String enteredUsername;
String enteredPassword;
while(correctLogin != true){
System.out.println("Enter Username: ");
enteredUsername = scan.nextLine();
System.out.println("Enter Password: ");
enteredPassword = scan.nextLine();
if(enteredUsername.equals("username") && enteredPassword.equals("passw00rd")){
System.out.println("You have entered the correct login info");
correctLogin = true;
break;
}
else{
System.out.println("Your login info was incorrect, please try again");
}
}
System.out.println("You are now logged in, good job!");
I want it so that when I type the password, it will automatically change into an asterisk.

try with this for password read:
Console console = System.console();
if(console != null){
console.readPassword("Enter Password: ");
}

I also had the same issue with my console java application and
I also do not want to display password in my IDE for security reasons.
So, to find the bug I had to debug against the productive environment. Here is my solution that works for me in IntelliJ IDEA:
public static String getPassword() {
String password;
Console console = System.console();
if (console == null) {
password = getPasswordWithoutConsole("Enter password: ");
} else {
password = String.valueOf(console.readPassword("Enter password: "));
}
return password;
}
public static String getPasswordWithoutConsole(String prompt) {
final JPasswordField passwordField = new JPasswordField();
return JOptionPane.showConfirmDialog(
null,
passwordField,
prompt,
JOptionPane.OK_CANCEL_OPTION,
JOptionPane.QUESTION_MESSAGE) == JOptionPane.OK_OPTION ? new String(passwordField.getPassword()) : "";
}

I am not sure if i get your question correctly, but still I will try to explain of what I understood.
To ensure that you see *** on the user screen you need to have some kind of a User interface written in HTML. I think in this case you are running your code in eclipse and via some kind of a main method. If that is the case then as Vince mentioned there is no benefit of ** since the letters would appear in the console.
What I would recommend is look for something basic web application tutorial and you would have more idea on how it works then.
HTH

Java .txt username and password not working [closed]

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Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 1 year ago.
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I was just experimenting with java (NetBeans) and I though up a quick text based adventure game. I'm trying to get it to check for your username and password in two text files "users.txt" and "passwords.txt" and i was following a guide on Cave of Programming
Here are the imports
import java.io.*;
import javax.swing.JFrame;
This is where the errors are,
private void loginActionPerformed(java.awt.event.ActionEvent evt) {
String usernametxt = "users.txt";
String passwordtxt = "passwords.txt";
String user = null;
String pass = null;
try {
// file reader for username \\
FileReader fileReader = new FileReader(usernametxt);
// file reader for password \\
FileReader fr = new FileReader(passwordtxt);
// buffered reader for username \\
BufferedReader bufferedReader = new BufferedReader(fileReader);
// buffered reader for password \\
BufferedReader br = new BufferedReader(fr);
// check for if user doesn't equal null \\
while((user = bufferedReader.readLine()) != null){
// if username equals first line of username.txt \\
if (username.getText().equalsIgnoreCase(user)){
// check for if pass doesn't equal null \\
while((pass = br.readLine()) != null){
// if password equals first line of passwords.txt \\
if (password.getPassword().equals(pass)){
// if password = pass than it will exit \\
System.exit(1);
}
// else continue \\
else{
continue;
}
}
}
}
bufferedReader.close();
br.close();
}
catch(FileNotFoundException ex){
System.out.println("Unable to open file ");
}
catch(IOException ex){
System.out.println("Error reading file");
}
}
Here are the text files
users.txt
matthew
passwords.txt
matt
Full code available here
http://textuploader.com/57urs
Newest Code Here
http://textuploader.com/577qk
feel free to ask me questions here.
Thank you for the help in advance!
Newest Code
private void loginActionPerformed(java.awt.event.ActionEvent evt) {
String usernames = username.getText();
String passwords = password.toString();
boolean signedin = false;
String usernametxt = "users.txt";
String passwordtxt = "passwords.txt";
String user = null;
String pass = null;
try {
FileReader fr1 = new FileReader(usernametxt);
FileReader fr2 = new FileReader(passwordtxt);
BufferedReader br1 = new BufferedReader(fr1);
BufferedReader br2 = new BufferedReader(fr2);
System.out.println("Username: "+br1.readLine());
System.out.println("Password: "+br2.readLine());
// While loops not running (not a if statement error \
while ((user = br1.readLine()) != null){
// checks if username is not equal to usernames.txt \\
if (user.equalsIgnoreCase(usernames)){
System.out.println("while loop running, username (right)");
break;
}
else{
System.out.println("while loop running, username (wrong)");
}
}
br1.close();
while ((pass = br2.readLine())!= null){
if (pass.equalsIgnoreCase(passwords)){
signedin = true;
System.out.println("While loop running, password (right)");
break;
}
else{
System.out.println("While loop running, password (wrong)
}
}
br2.close();
// Commented out the if statements because i dont want to to close while testing \
// if (signedin){
// System.out.println("SIGNEDIN = TRUE");
// new error1().setVisible(true);
// this.dispose();
// }
// if (!signedin){
// System.out.println("SIGNEDIN = FALSE");
// System.exit(1);
// }
}
catch(FileNotFoundException ex){
System.out.println("Unable to open file ");
}
catch(IOException ex){
System.out.println("Error reading file");
}
}
New Problem
The while loops do not run, this is confirmed when it doesn't print "While loop running, User/Pass", This is not a if/then statement error as I have added the else statement to print if the username is right or wrong. Please help, Thanks Matthew.

If i understood it correctly:
Two files:
users.txt holds the usernames.
passwords.txt holds the passwords.
We want:
Keep reading the user file until the file ends or we've found our user.
Read the corresponding line on the password file and check if the password matches.
Checking the code, while((user = bufferedReader.readLine()) != null) does the first part nicely. We DO want to keep reading the entire file trying to find our user, right?
but the nested while seems a bit fishy. We only need to check a SINGLE password for a given user, right? RIGHT?
Digging a bit deeper into your code, we see:
if (password.getPassword().equals(pass)) {
// if password = pass than it will exit
System.exit(1);
} // plus Lots of code...
Hey! I don't think System.exit does what you're looking for!
System.exit will exit the program, going back to DOS or whatever the cool kids are using these days. The integer it returns is called an error code, and can be used to feed info back to the terminal/shell that started our program.
The keyword you're most likely looking for is break: that will exit a given loop pronto, no questions asked.
Let's do some break/continue mashups! Suppose we "Win at life" if the password is indeed correct:
boolean winAtLife = false;
while((user = bufferedReader.readLine()) != null){
String candidatePassword = br.readLine();
if (candidatePassword == null) {
// So the password file is shorter than the userfile?
// We probably want to log or alert the poor DevOp guys.
// throwing an exception seems like the right thing to do here!
break;
}
if (!user.equalsIgnoreCase(username.getText())) {
// These are not the droid we're looking for, Better luck next line!
continue;
// Also notice that, since we KNOW that user can't be null,
// we're using the force to save ourselves from dreaded NullPointerExceptions!
}
if (!candidatePassword.equals(password.getPassword())) {
// Hmmm, wrong password, I guess?
// Not sure what do do next, but we DO NOT need to keep looping
// since we've found our droid/user/whatever.
// So let's break and save some EC2 Cycles.
break;
}
// If we ever reach here, we got ourselves a winner!
pass = candidatePassword
winAtLife = true;
}
EDIT: Ok... So I've heard that:
The cool kids use Scanner nowadays.
Auto-closing resources is good for our health.
Something about separation of concerns and mixing domain-code with the UI. In code samples. Whatever.
So here we go, take two, now as a method:
public boolean checkCredentials(String username, String password) throws IOException {
// these two are begging to be constants or inlined.
final String usernametxt = "users.txt";
final String passwordtxt = "passwords.txt";
if (username == null || password == null) {
// You probably don't want this in production code.
// Exceptions are your best friends when something unexpected occurs.
return false;
}
try (final Reader fileReader = new FileReader(usernametxt);
final Reader passwordReader = new FileReader(passwordtxt)) {
Scanner userScanner = new Scanner(fileReader);
Scanner passwordScanner = new Scanner(passwordReader);
while(userScanner.hasNext()) {
final String user = userScanner.next();
if (!passwordScanner.hasNext()) {
// So the password file is shorter than the userfile?
// We probably want to log or alert the poor DevOp guys.
// throwing an exception seems like the right thing to do here!
return false;
}
final String candidatePassword = passwordScanner.next();
if (!user.equalsIgnoreCase(username)) {
// This is not the droid we're looking for
// Also notice that, since we KNOW that user can't be null,
// we're using the force to save ourselves
// from dreaded NullPointerExceptions!
continue;
}
if (!candidatePassword.equals(password)) {
// Hmmm, wrong password, I guess?
// Not sure what do do next, but we DO NOT need to keep looping
// So let's return early and save some EC2 Cycles.
return false;
}
// If we ever reach here, we got ourselves a winner!
return true;
}
} // yay for autocloseable
return false;
}

Code works in Netbeans, but not TextPad?

Here is the code throwing the error. In TextPad, I get a NullPointerException when I try to write the contents of the array to the text file. (It doesn't see anything in the array.) Note: it works perfectly in Netbeans. I only get this in Textpad. I have scoured Google and i have no idea why it is doing this.
void enterContact(){
// test contact
contactName = nameField.getText();
if (contactName == null || contactName.equals(""))
{
JOptionPane.showMessageDialog(null, "Please enter a name.");
return;
}
//test age betweeen 0 and 120
contactAge = ageField.getText();
try{
Integer.parseInt(contactAge);
}
catch(NumberFormatException e){
JOptionPane.showMessageDialog(null, "Please enter a valid age.");
}
finally{
if (Integer.parseInt(contactAge) <= 0 || Integer.parseInt(contactAge) >= 121){
JOptionPane.showMessageDialog(null, "Please enter a valid age.");
return;
}
}
// test email
contactEmail = emailField.getText();
if ( contactEmail == null || contactEmail.equals(""))
{
JOptionPane.showMessageDialog(null, "Please Enter an Email Address.");
return;
}
//test cell number
contactPhone = phoneField.getText();
try
{
Integer.parseInt(contactPhone);
}
catch(Exception e) {
JOptionPane.showMessageDialog(null, "Please Enter a valid Phone Number.");
return;
}
String columns2[] = { contactName, contactAge, contactEmail, contactPhone };
//write data to file
try{
for (int i = 0; i < columns2.length; i++){
fw.write(columns2[i].toString() + ", ");
}
fw.write("\r\n");
fw.flush();
fw.close();

If you get NullPointerException during writing in file, there is two possibilities:
You may not open the file. For example because of forgetting calling the constructor of FileWriter.
You don't have any permission to open the file and write into it.
If you got the exception only when you are run it using TextPad, I think the second problems occurred. You don't have permission.

Try To run your TextPad in Administrator Mode
Right Click on Textpad icon -> Run as administrator
& then RUN above program
i sure your program get executed properly.

Pass a string from one class to another in java

I'm trying to pass a String from one class to another class but the result I'm getting is 'null'. I want to pass the String username from LoginFrame to HomeworkFrame;
HomeworkFrame:
public void loadSubjects (){
String item;
try{
System.out.println(username);
Scanner f = new Scanner (new FileReader (username + " " + "Subjects" + ".txt"));
while(f.hasNext()){
item = f.nextLine();
chSubjects.add(item);
}
f.close();
}catch(Exception e){
JOptionPane.showMessageDialog(null, "Subjects cannot be loaded!", "Error", JOptionPane.ERROR_MESSAGE);
}
}
LoginFrame:
public void loginUser(){
r = new Registration();
h = new HomeworkFrame();
l = new Login();
l.username = txtUser.getText();
l.password = txtPass.getText();
try{
String line;
boolean passwordFound = false ;
BufferedReader f = new BufferedReader(new FileReader(l.username + ".txt"));
while((line = f.readLine()) != null){
if(line.equals(l.password)){
passwordFound = true;
}
}
if(passwordFound){
h.username = l.username;
dispose();
m.setSize(700,600);
m.setLocation(100,100);
m.setVisible(true);
}else{
JOptionPane.showMessageDialog(null, "Wrong information!", "Error", JOptionPane.ERROR_MESSAGE);
}
f.close();
}catch(Exception e){
JOptionPane.showMessageDialog(null, "Wrong information!", "Error", JOptionPane.ERROR_MESSAGE);
}
}
Obviously I'm getting the error "Subjects cannot be loaded" as the username is null(I checked it by using the println method).

In case problems like this you have to track your variables/fields from the place you've noticed your 'username' field is null. Next steps should be:
Check what operations you do on 'h' object before you call the loadObjects() method and if any then check what influence they have on username field in HomeWorkFrame (using println or a debugger).
Check if your passwordFound in LoginFrame is true (because if it's false it doesn't assign a value to h.username)
If it's false check if your password's been retrieved from a file (using same println statement)
This kind of scenario should help you finding most of 'null' bugs.

Try to check first, which type of Exception you get.
May be the file is not existing or the list is null or....

Is a format problem : put a \ before your space in pathString : "\ "
You have to write it "\ Subjects.txt", without '+' between.

public class LoginFrame{
private HomeworkFrame hw;
public void doSomething(){
String username = "your username";
hw = new HomeworkFrame(username);
}
}
public class HomeworkFrame{
public HomeworkFrame(String username){
doSomething with 'username'
}
}
Ans to your question! :)

If System.out.println(username); displays null this means that
1.username variable is not initialized and left.
2.value is not assigned to it properly.
3.It might be a static variable and you are changing the value of it.
Please check all these conditions and please give that part of the code from where the loadSubjects() is being called, and not the body of that method as you have provioded it already.
Also all those parts of code where the username is initialized,assigned,modified.

It is required to specify or pass the value otherwise it will definitely give Null as it will not find any value to execute.