Java JTextField在内部类的方法调用中不起作用

Question

I'm building a GUI and am trying to implement a very simple search - when you input a SSN, it checks to see if there's a customer with that SSN. I have a JTextField where the SSN is entered, and when you click submit, it calls the searchBySSNString method and returns true or false. The problem is, whenever I pull text from the JTextField, it returns false.

For the sake of this question, I've tried to boil this down to as little code as I reasonably can so someone doesn't have to wade through all of my code. I have extra code included in the problem portion to show what I've been working through. If I hard code a string in and search for it, it returns true, and if I compare that hard coded string to the text from the JTextField, it returns 0 if the same text is typed in.

A few miscellaneous notes: I use SSN as a string because I don't think I'll ever need to manipulate it like it's a number. If that's a bad idea, I'd like to know why. The SSN on the account created is 222222222. I don't have anything implemented to validate the input or to account for dashes or anything yet.

As you'll see if you actually slog through my code, I'm quite the beginner, so I'm always willing to listen to any tips anyone has, but the pressing problem now is figuring out why the input from the JTextField will not work in the search.

import java.util.ArrayList;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JTextPane;

public class Bank {

    private JFrame frame;
    private JTextField txtSearchBySSN;
    private JTextField txtTestMessage;
    static ConnectionFactory connectionFactory = ConnectionFactory.getConnectionFactory();

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        connectionFactory.newAccountAndCustomer("Mike", "222222222");

        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Bank window = new Bank();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public Bank() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setBounds(100, 100, 607, 429);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);

        JLabel lblSearchBySSN = new JLabel("Search for customer by SSN");
        lblSearchBySSN.setBounds(6, 38, 190, 16);
        frame.getContentPane().add(lblSearchBySSN);

        txtSearchBySSN = new JTextField();
        txtSearchBySSN.setBounds(208, 32, 134, 28);
        frame.getContentPane().add(txtSearchBySSN);
        txtSearchBySSN.setColumns(10);

        //here's the problem portion
        JButton btnSearchBySSN = new JButton("Search");
        btnSearchBySSN.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                //get text from the textbox
                String testString = txtSearchBySSN.getText();
                //print out the text from the textbox to see if it looks the same
                System.out.println(testString);
                //call the search method using the string from the textbox
                System.out.println(connectionFactory.searchBySSNString(testString));
                //call the search method using two hard-coded string to see if the method works
                //one that does match and one that doesnt
                System.out.println(connectionFactory.searchBySSNString("222222222"));
                System.out.println(connectionFactory.searchBySSNString("333333333"));
                //compare the text from the textbox to a hard-coded string - this returns 0
                System.out.println(testString.compareTo("222222222"));
            }
        });
        btnSearchBySSN.setBounds(355, 33, 117, 29);
        frame.getContentPane().add(btnSearchBySSN);

        txtTestMessage = new JTextField();
        txtTestMessage.setBounds(117, 83, 134, 28);
        frame.getContentPane().add(txtTestMessage);
        txtTestMessage.setColumns(10);
    }
}

class ConnectionFactory {
    private ArrayList<Customer> customers;
    private ArrayList<Account> accounts;
    private ArrayList<Connection> connections;
    private static ConnectionFactory connectionFactory;

    private ConnectionFactory() {
        customers = new ArrayList<Customer>();
        accounts = new ArrayList<Account>();
        connections = new ArrayList<Connection>();
    }

    //creates a ConnectionFactory if one doesn't already exist
    public static ConnectionFactory getConnectionFactory() {
        if (connectionFactory == null) {
            connectionFactory = new ConnectionFactory();
        }
        return connectionFactory;
    }

    //create new account and new customer
    public void newAccountAndCustomer(String customerName, String ssn) {
        Customer customer = new Customer(customerName, ssn);
        Account account = new CheckingAccount();

        //create the connection object, add all of the items to their respective arrays
        Connection connection = new Connection(customer, account);
        customers.add(customer);
        accounts.add(account);
        connections.add(connection);
    }

    //check to see if customer exists
    public String searchBySSNString(String ssn) {
        boolean customerExists = false;

        for(int i = 0; i < customers.size(); i++) {
            if(customers.get(i).getSSN() == ssn) {
                customerExists = true;
                break;
            }
        }
        if (customerExists) {
            return "true";
        }
        else {
            return "false";
        }
    }
}

abstract class Account {
    private long accountNumber;
    private double currentBalance;

    protected Account() {
        //
    }

    protected Account(double currentBalance) {
        this.currentBalance = currentBalance;
    }

    public void withdraw(double withdrawalAmount) {
        currentBalance -= withdrawalAmount;
    }

    public void deposit(double depositAmount) {
        currentBalance += depositAmount;
    }

    public double getCurrentBalance() {
        return currentBalance;
    }

    public void setCurrentBalance(double newBalance) {
        this.currentBalance = newBalance;
    }

    public long getAccountNumber() {
        return accountNumber;
    }

    public void setAccountNumber(long accountNumber) {
        this.accountNumber = accountNumber;
    }
}

class CheckingAccount extends Account {
    private double overdraftAmount;
    private static long nextAccountNumber = 10000000;
    private long accountNumber;

    public CheckingAccount() {
        accountNumber = nextAccountNumber;
        nextAccountNumber++;
    }

    public void setOverdraftAmount(double overdraftAmount) {
        this.overdraftAmount = overdraftAmount;
    }

    public double getOverdraftAmount() {
        return overdraftAmount;
    }

    public long getAccountNumber() {
        return accountNumber;
    }

    @Override
    public String toString() {
        return String.valueOf(accountNumber);
    }
}

class Connection {
    private Customer customer;
    private Account account;

    public Connection(Customer customer, Account account) {
        this.customer = customer;
        this.account = account;
    }

    public void setCustomer(Customer customer) {
        this.customer = customer;
    }

    public Customer getCustomer() {
        return customer;
    }

    public void setAccount(Account account) {
        this.account = account;
    }

    public Account getAccount() {
        return account;
    }   
}

class Customer {
    private String name;
    private String ssn;

    public Customer(String name, String ssn) {
        this.name = name;
        this.ssn = ssn;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setSSN(String ssn) {
        this.ssn = ssn;
    }

    public String getSSN() {
        return ssn;
    }

    @Override
    public String toString() {
        return name;
    }
}

Answer 1

if(customers.get(i).getSSN() == ssn)

Problem is in this line. Use equals() method for string comparison instead of ==.

If you use == to compare strings, it will return true if both String objects' locations in memory are same. But equals() method will check values of those String objects. So changing above line with

if(customers.get(i).getSSN().equals(ssn))

will fix your problem.

Answer 2

Actually i don't read all of your code, but the way you compare observational equality between objects in Java is with equals method, == is just reference equality. So

Change:

if(customers.get(i).getSSN() == ssn)

to

if(customers.get(i).getSSN().equals(ssn))

Also don't use null layout. Swing was designed to use with Layout Managers.

Read more in:

How do i compare strings in java

Using layout managers