我正在构建一个GUI并尝试实现一个非常简单的搜索 - 当您输入SSN时，它会检查是否有客户使用该SSN。我有一个输入SSN的JTextField，当你单击submit时，它会调用searchBySSNString方法并返回true或false。问题是，每当我从JTextField中提取文本时，它都会返回false。
为了这个问题，我试图将其归结为尽可能少的代码，因此有人不必涉及我的所有代码。我在问题部分中包含了额外的代码，以显示我一直在做的工作。如果我对字符串进行硬编码并搜索它，它将返回true，如果我将该硬编码字符串与JTextField中的文本进行比较，则在输入相同文本时返回0。
一些杂项说明：我使用SSN作为字符串，因为我不认为我需要操纵它，就像它是一个数字。如果那是个坏主意，我想知道原因。创建的帐户上的SSN是222222222.我没有任何实现来验证输入或解决破折号或任何其他内容。
正如你会看到你是否真的在我的代码中跋涉，我是初学者，所以我总是愿意倾听任何人提出的任何提示，但现在紧迫的问题是弄清楚为什么输入来自JTextField将无法在搜索中使用。
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;
}
}
答案 0 :(得分：2)
if(customers.get(i).getSSN() == ssn)
问题出在这一行。使用equals（）方法进行字符串比较而不是==。
如果使用==来比较字符串，如果两个String对象在内存中的位置相同，它将返回true。但是equals（）方法将检查那些String对象的值。所以用
改变上面一行if(customers.get(i).getSSN().equals(ssn))
将解决您的问题。
答案 1 :(得分：2)
实际上我没有阅读你的所有代码，但是你比较Java中对象之间的观察相等性的方式是使用equals方法，==只是引用相等。所以
变化：
if(customers.get(i).getSSN() == ssn)
到
if(customers.get(i).getSSN().equals(ssn))
也不要使用null布局。 Swing旨在与布局管理器一起使用。
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