Java 如何找到一个元素?
如何检查集合中的元素是否存在Java 如何找到一个元素?,java,servlets,set,Java,Servlets,Set,如何检查集合中的元素是否存在 public class Account { public Account(String username, String password, String lastname, String firstname){ this.username = username; this.password = password; this.firstname = firstname; this.lastna
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, "", "","");
/*
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");
for (Account p : acc)
{
if(p.equals(act1){
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();
}
设置为继续。”);
}
否则{
打印(“输入的用户帐户无效。单击以登录”);
}
}
输出。打印(“”);
输出。打印(“”);
out.close();
}
集合有一个“contains”方法以及任何扩展/实现集合的类型。在为帐户类型实现equals和hashcode时必须小心。您可以在文档中找到详细信息。覆盖equals(对象)
(使用正确的实现)在您的帐户中
类,然后执行以下操作:
boolean containsAccount = acc.contains(some_account)
其中,
some\u account
是account
的实例,请阅读HashSet
的Javadoc。我将在我的servlet中计算containsAccount?@KarlxSwanovski正确吗