We Keep Coding

How can I create a loop to search through an object for the correct value in java?

I'm attempting to search through an object to see if a user's input matches what the program has stored, but I cannot figure out a way to make it work. I attempted to see if the value inputed by a user matched that of one in the userID spot for any of these Employee objects, but that didn't work. For example, here is the object:
Employee{userID='u1234567', userSalary=65000, userType=true}
Employee{userID='u1938562', userSalary=100000, userType=true}
Employee{userID='u1047218', userSalary=125000, userType=false}
Employee{userID='u1530078', userSalary=55000, userType=true}
Employee{userID='u1088621', userSalary=78400, userType=true}
Employee{userID='u2405234', userSalary=105000, userType=false}
Employee{userID='u1142592', userSalary=87500, userType=true}
Employee{userID='u1000092', userSalary=235000, userType=true}
Employee{userID='u1220433', userSalary=450000, userType=false}
Employee{userID='u1082304', userSalary=95000, userType=true}
My first function attempts to match the user's input with one of the userID's, but like I said it only works with the "u1234567"'s line. I have been attempting this for quite a while now, but I am relatively new to java and so I'm still learning. Below is my code, and where I commented out the "This is where I'm trying to loop through objects to look for a match" is where I would think to place this code, but I would greatly appreciate any feedback or better suggestions.
package homework4;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.lang.reflect.Array;
import java.util.Scanner;
import java.util.ArrayList;
import java.util.Arrays;
public class main {
public static void main(String[] args) throws Exception {
// pass the path to the file as a parameter
Scanner file_in = new Scanner(new File("input.txt"));
Scanner in = new Scanner(System.in);
ArrayList<Employee> employees = new ArrayList<>();
// CREATE NEW ARRAY LIST FOR THE USERS
while (file_in.hasNextLine()) {
boolean isWorker = false;
String current_line = file_in.nextLine();
String[] line_split = current_line.split(",");
if (line_split[2].equals("1")) {
isWorker = true;
}
//Load the data To the List
employees.add(new Employee(line_split[0], Integer.parseInt(line_split[1]), isWorker));
}
ArrayList<Employee> copyEmployeesList1 = new ArrayList<>();
String userID = null;
//loop 4 times then create output.txt
for(int i = 0; i < 4; i++) {
// This is where I'm trying to loop through the object to look for a match
for(int b = 0; b < employees.size(); b++) {
employees.get(userID);
}
// User inputs userID and checks to see if theres a match
System.out.println("Enter employee ID of an employee?");
userID = in.nextLine();
for (Employee employee : employees){
if (employee.getUserID().equalsIgnoreCase(userID)) {
copyEmployeesList1.add(employee);
//System.out.println(employee);
break;
} else {
System.out.println("Incorrect value, please try again");
System.out.println("Enter employee ID of an employee?");
userID = in.nextLine();
break;
}
}
// User inputs user salary and checks if it matches the previous userID's lines salary.
System.out.println("Enter salary of the employee");
String userSalary = in.nextLine();
int userInput = Integer.parseInt(userSalary);
if(userInput == copyEmployeesList1.get(0).getUserSalary()) {
} else {
System.out.println("Incorrect value, please try again");
System.out.println("Enter salary of the employee");
}
// Redundant input my professor requires, but input a 1 or a 2
System.out.println("Is this in a manager or worker? (Enter 1 for worker 2 for manager)");
String userType = in.nextLine();
boolean choice;
choice = userType.equals("1");
employees.add(new Employee(userID, Integer.parseInt(userSalary), choice));
}
//compile salaries
for(Employee emp:employees) {
ManagerEmployee.calculate(emp);
WorkerEmployee.calculate(emp);
}
employees.forEach(System.out::println);
}

employees is an arraylist of Employee, you can only use .get to get by a specific index. You will need to use something like javas stream filter or a different method like in this tutorial.
ArrayList<Employee> employeesWithASpecificID = users.stream()
.filter(employee -> employee.getUserID() == userID)
.collect(Collectors.toList());

Error while using database in Java using SQLite

Bank class calling the Atm class.The machine class contains the start machine method. Here onwards loop will run forever calling the required methods from another classes not relevant. The create table method should be called only once.Once the Pin is validated the program runs infinitely
import java.util.Scanner;
public class Bank {
final static int PIN = 5423;//pin to start the ATM operations
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Enter the PIN to start the machine");
for(int i = 3; i >= 1;--i) {
int n = scanner.nextInt();
if(n == PIN) {//if pin was correct , start the ATM
Atm atm = new Atm();
atm.startMachine();
break;
}
else if(i > 1)
System.out.println("Incorrect PIN. You have " + (i-1) + " tries remaining");
else {
System.out.println("Tries exhausted. Contact the main office.");
break;
}
}
scanner.close();
}
}
Atm class which has start machine method
class Atm {//class for functioning of ATM
Scanner scan;
protected String load;//loading time
protected int cashAvailable = 2000000;//initial cash available
static Database database;
Atm(){//constructor to initialize fields
scan = new Scanner(System.in);
load = "00:00";//the loading time at midnight
database = new Database();
database.createTable();//call the database class
}
public void startMachine(){//start the machine
Machine machine = new Machine();
machine.start();//call the start method
}
}
And the machine class
public void start() {//method to start the machine
Withdraw withdraw = new Withdraw();//withdraw object
Deposit deposit = new Deposit();//deposit object
while(true) {//infinite loop for functioning of machine
String currentTime = new SimpleDateFormat("HH:mm").format(new Date());//get the current time
boolean isLoadingTime = currentTime.equals(load);//if is loading time
if(isLoadingTime) {//if yes, the call load method
load();//method to load the cash
}
//show the welcome screen at every iteration
System.out.println("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");
System.out.println();
System.out.println("Welcome to National Bank");
SimpleDateFormat formatter = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
Date date = new Date();
System.out.print(formatter.format(date) + " ");
System.out.println(LocalDateTime.now().getDayOfWeek());
System.out.println("Press 1 to view your current balance");
System.out.println("Press 2 to withdraw cash");
System.out.println("Press 3 to deposit funds");
System.out.println();
System.out.println("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");
while(true) {
int enter_num = scan.nextInt();//get the preferred choice
if(enter_num == 1) {
currentBalance();//method to show current balance
break;
}
else if(enter_num == 2) {
withdraw.debit();//method to withdraw cash
break;
}
else if(enter_num == 3) {
deposit.giveCash();//method to deposit cash
break;
}
else
break;//if not valid option
}
}
}

The obvious errors in your code in update() method are the comma after SET Balance = ? which you must remove and also change the indices of stmt.setInt() to 1 for balance and 2 for accountNo because you are passing 2 paremeters with that order in your UPDATE statement:
String change = "UPDATE accounts SET Balance = ? WHERE AccountNumber = ?";
try {
PreparedStatement stmt = conn.prepareStatement(change);
stmt.setInt(1,balance);
stmt.setInt(2,accountNo);
.............................
Also, the error message:
Abort due to constraint violation (UNIQUE constraint failed:
accounts.AccountNumber)
means that you are trying to insert in the table an account number that already exists in the table and this is not allowed because the column AccountNumber is the primary key of the table so it is unique.
Also, inside createTable() what is sc? Is it a resultset?
If so, what are you trying to do? Are you trying to loop through the rows of the table?
The table is just created and it is empty.
From the code that you posted, I can't see why you get 4 times the message "A new database has been created", because I don't know how you call the method createTable().

Exception handling in JTextField

I am writing a restaurant application.
In this part, in order to add cook, user needs to enter cook's name in a nameTextField and cook's salary in a salaryTextField and at the name part I want to prevent the user from entering numbers and at the salary part I want to prevent the user from entering words. For salary part I tried to use exception handling but couldn't really succeed.
class AddButtonInCookClick implements ActionListener{
public void actionPerformed(ActionEvent e) {
String name = (String)nameTextFieldCook.getText();
double salary = new Double(0.0);
try {
salary = Double.parseDouble(salaryTextField.getText());
}catch(NumberFormatException ex) {
System.out.println(ex);
}
restaurant.getEmployees().add(new Cook(id, name, salary));
id++;
JOptionPane cookOptionPane = new JOptionPane();
JOptionPane.showMessageDialog(cookOptionPane, "Cook added succesfully.");
}
}
addButtonInCook.addActionListener(new AddButtonInCookClick());
Even though the program doesn't crush. I still can't make user enter numbers for salary part. Thank you for helping.

You can restrict input solely to numerals by using JFormattedTextField in lieu of a normal JTextField.
Sample code:
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import java.text.NumberFormat;
import javax.swing.text.NumberFormatter;
public class Test extends JFrame
{
JFormattedTextField salaryFormattedTextField;
NumberFormat numberFormat;
NumberFormatter numberFormatter;
public Test()
{
numberFormat = NumberFormat.getInstance();
// delete line if you want to see commas or periods grouping numbers based on your locale
numberFormat.setGroupingUsed(false);
numberFormatter = new NumberFormatter(format);
numberFormatter.setValueClass(Integer.class);
// delete line if you want to allow user to enter characters outside the value class.
// Deleting the line would allow the user to type alpha characters, for example.
// This pretty much defeats the purpose of formatting
numberFormatter.setAllowsInvalid(false);
salaryFormattedTextField = new JFormattedTextField(formatter);
this.add(salaryFormattedTextField);
}
public static void main(String[] args)
{
Test test = new Test();
s.pack();
s.setVisible(true);
}
}
The alternative, using the code structure you already have, is to throw up a JOptionPane when the input doesn't parse correctly.
try
{
salary = Double.parseDouble(salaryTextField.getText());
restaurant.getEmployees().add(new Cook(id, name, salary));
id++;
JOptionPane cookOptionPane = new JOptionPane();
JOptionPane.showMessageDialog(cookOptionPane, "Cook added succesfully.");
}
catch(NumberFormatException ex)
{
JOptionPane cookFailPane = new JOptionPane();
JOptionPane.showMessageDialog(cookFailPane , "Could not add cook. Please enter salary using only numeric input.");
ex.printStackTrace();
}

How do I keep asking the user for input if the input wasn't a number?

I'm making a cash register with an "other" option, which allows the user to add an amount through user input. I have done this with a JOptionPane, the "other" button code is the following:
private void btnOverigActionPerformed(java.awt.event.ActionEvent evt) {
String prijs = JOptionPane.showInputDialog(this, "Vul een bedrag in");
try {
double overigePrijs = Double.parseDouble(prijs);
if (overigePrijs > 0){
aantalProducten[6]++;
totaalPerProduct[6] += overigePrijs;
}
huidigePrijsDisplay();
}
catch (Exception letter){
while (true){
prijs = JOptionPane.showInputDialog(this, "Vul a.u.b. alleen cijfers in.");
}
}
This while-loop will not close the JOptionPane, even when inputting numbers, how do I loop this correctly?
Edit after almost finishing my SE studies:
I was missing an if-statement in my while-loop. What I was trying to do was checking if the input of prijs were only numbers and if not, keep showing the dialog. I never got around to fixing this because it's an old project but I should have stated the motivation behind the code more clearly!

The question is not clear itself. What I assume that if the try part does not run as you wish, the JOptionPane should reopen and user should be prompted to do it again. If it is so, you can do the following:
Create a method:
private void doTheTask(){
String prijs = JOptionPane.showInputDialog(this, "Vul een bedrag in");
try{
//your task here.
}
catch (Exception letter){
//Call the method again.
doTheTask();
}
}
And call the method inside your action:
private void btnOverigActionPerformed(java.awt.event.ActionEvent evt){
doTheTask();
}

I suggest you a different approach in your code:
String prijs = "";
double overigePrijs = -1;
while (true) {
prijs = JOptionPane.showInputDialog(null, "Vul een bedrag in");
if (prijs != null) { // if user cancel the return will be null
try {
overigePrijs = Double.parseDouble(prijs);
break; // Exits the loop because you have a valid number
} catch (NumberFormatException ex) {
// Do nothing
}
} else {
// You can cancel here
}
// You can send a message to the user here about the invalid input
}
if (overigePrijs > 0) {
aantalProducten[6]++;
totaalPerProduct[6] += overigePrijs;
}
huidigePrijsDisplay();
This code will loop until the user enters a valid number and then you can use after the while loop. Some improvement may be necessary like a cancel logic or change the message on the second time but the main idea is this.

Show an item in a JScrollPane

I store in an arraylist an object (contact) which has name,number,email.
Then i want to display lets say the name in ScrollPane but i get an error on retrieving it (from my other class).
What im doing wrong?
Heres this part of the code(i get the error in the last line using the ):
class GetUserInput implements ActionListener {
//It's the reactions to the buttons that are pressed
public void actionPerformed(ActionEvent event) {
if (event.getActionCommand().equals("Add Contact")) {
Agenda a = new Agenda();
System.out.println(event);
String inp = JOptionPane.showInputDialog("Enter your contact name");
a.setName(inp);
String inp1 = JOptionPane.showInputDialog("Enter your contact number");
a.setPhoneNumber(inp1);
String inp2 = JOptionPane.showInputDialog("Enter your contact email");
a.setEmail(inp2);
contacts.add(a);
} else if (event.getActionCommand().equals("Edit Contact")) {
String inp = JOptionPane.showInputDialog("Enter the name of the contact you wish to edit ");
} else if (event.getActionCommand().equals("Show All Contacts")) {
System.out.println(a.getName());

You can't run it, because a is created in another block. You can't access it in the last else if-block before creating and assigning a new Variable a.