比较使用参数的对象时总是返回错误

问题描述：

我不知道为什么与使用该参数的帐户进行比较时总是返回false。它只有在帐号被硬编码时才会返回true。比较使用参数的对象时总是返回错误

public class Account 
{ 
    public Account(String username, String password, String lastname, String firstname){ 
     this.username = username; 
     this.password = password; 
     this.firstname = firstname; 
     this.lastname = lastname; 
    } 

    public String getUsername() { 
     return username; 
    } 

    public String getPassword() { 
     return password; 
    } 

    public String getFirstname() { 
     return firstname; 
    } 

    public String getLastname() { 
     return lastname; 
    } 


    private String username; 
    private String password; 
    private String firstname; 
    private String lastname; 
    public boolean equals(Object obj) 
    { 
     boolean result = false; 
     if (obj != null && obj instanceof Account) 
     { 
      Account p = (Account)obj; 
      if (getUsername().equals(p.getUsername()) 
       && getPassword() == p.getPassword()) 
      { 
       result = true; 
      } 
     } 
     return result; 
    } 
}

我的servlet

Set<Account> acc = new HashSet<Account>(); 

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
     doPost(request, response); 
    } 

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
     response.setContentType("text/html"); 
     acc.add(new Account("test1", "pass123", "Boom", "Bang")); 
      acc.add(new Account("test2", "pass123", "Beam", "Beng")); 
     PrintWriter out = response.getWriter(); 
     String username = ""; 
     String password = ""; 


    if(request.getParameter("Username") != null){ 
     username = request.getParameter("Username"); 
    } 
    if(request.getParameter("Password") != null){ 
     password = request.getParameter("Password"); 
    } 

    Account act1 = new Account(username, password, "", "",""); 
      System.out.print(username+password); // test if the username and password change based on the parameter 
      /* 
      Works only on hard code 
      Account act1 = new Account("test1", "pass123", "", "",""); 
      */ 

     out.print("<html>"); 
     out.print("<head><link href='layoutit/css/bootstrap.min.css' rel='stylesheet'>" 
       + "<link href='layoutit/css/style.css' rel='stylesheet'>"); 
     out.print("<title></title>"); 
     out.print("</head>"); 
     out.print("<body"); 
     if(acc.contains(act1)){ // the condition that always return false if not hardcode 
       out.print("<h3>Click <a href='displayuser.html'>here</a> to continue.</h3>"); 
     } 
    else 
     out.print("<h1>Invalid user account entered.Click <a href='index.html'>here</a> to login.</h1>"); 
     out.print("</body>"); 
     out.print("</hmtl>"); 
     out.close(); 
    }

如果使用.equals代替==用于比较的密码是否行得通？ – immibis

感谢它的工作。我错过了。 :) –

因此在这里接受正确的答案... –

答

比较密码时使用.equals，而不是==。

答

密码也是字符串（从我对这个问题的评论复制），但使用的是==比较它，使用.equals。使用它，如下所示，从下：当您使用instanceof操作

 if (getUsername().equals(p.getUsername()) 
      && getPassword() == p.getPassword())

要

if (getUsername().equals(p.getUsername()) 
      && getPassword().equals(p.getPassword()))

而且，不需要单独的空检查。

所以，你可以在此线

if (obj != null && obj instanceof Account)

为

if (obj instanceof Account)

比较使用参数的对象时总是返回错误

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