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Conditional using a string in Java after using Scanner [duplicate]

This question already has answers here:
How do I compare strings in Java?
(23 answers)
Closed 4 years ago.
It always give the second conditional regardless of the input. Is (userName == "Charles") the correct way of doing this conditional? or do i need something else.
import java.util.Scanner;
public class Name_input {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String userName = input.next();
System.out.println(userName);
if (userName == "Charles")
{
System.out.println("Correct Name");
}
else if (userName != "Charles")
{
System.out.println("Incorrect Name");
}
}
}

Is (userName == "Charles") the correct way of doing this conditional
No You don't use "==" to compare strings.
Instead you should be using the equals(...) method:
if ( "Charles".equals( userName ) )
Note I reversed the order of the comparison. This will prevent a NPE if the username is ever null.
System.out.println(userName);
Does that display the expected value? Do you need to use the trim() method?
else if (userName != "Charles")
Also, there is no need for the "else if". The name is either "Charles" or it isn't so you don't need the additional "if" statement.

How to use if else to set var value in TextField

can I ask how I can instantly equal my TextField named txtUserName into 'Aime' and also my txtPassword equal to 'Joy' so that it will show the message "User Name and Password Match!" ? Anyone? Please help me :(
public void actionPerformed(ActionEvent e){
if (e.getSource()== btnClear){
txtUserName.setText("");
}
if(e.getSource() == btnLogin){
if (txtUserName.setText="Aime" && txtPassword.setText="JOy")){
JOptionPane.showMessageDialog(null, "User Name and Password Match!");
}
else {
JOptionPane.showMessageDialog(null, "User Name and Password Invalid!");
}

These are the Small modifications needed.
if (txtUserName.getText().equals("Aime") && txtPassword.getText().equals("Joy")){
JOptionPane.showMessageDialog(null, "User Name and Password Match!");
}else{
JOptionPane.showMessageDialog(null, "User Name and Password Invalid!");
}
For your reference : What is the difference between == vs equals() in Java?

you have two problems here:
txtUserName.setText="Aime" && txtPassword.setText="JOy"
am guessing you are trying to check the user input so you need to use the gettext method...
on the other hand you can not compare strings using ==, but furthermore you mistyped the == and are instead of comparing assigning, assignment that is invalid since you can not set the text of that view in that way...
try instead
txtUserName.getText().toString().equals("Aime") && ...

Multiple textfields with one joptionpane [duplicate]

This question already has answers here:
JOptionPane - check user input and prevent from closing until conditions are met
(2 answers)
Closed 6 years ago.
I want a user to input 4 things (first name, last name, email and phone number) and in case he misses one or more just one JOptionPane window would show.
String firstname = TF_1.getText();
String lastname = TF_2.getText();
String email = TF_3.getText();
String phonenumber = TF_4.getText();
if (TF_1.equals("") ||
TF_2.equals("") ||
TF_3.equals("") ||
TF_4.equals("")) {
JOptionPane.showMessageDialog(null, "All text fields must be filled");

First thing personally I don't like one generic message for all fields it puts users in confusion what they have not filled. You can use a flow that you check all field one by one and if a field is empty show error for it and return from their.
Secondly check on string fields firstname, lastname etc not on TF_1.
public boolean isEmpty(String... fields)
{
for (String string : fields)
{
if (null == string || string.trim().length() == 0)
{
// return true of filed is blank
return true;
}
}
return false;
}
You can use this method and pass all your fields to check if any of them is empty.

Simple login with Java code - using conditional assignment [duplicate]

This question already has answers here:
How do I compare strings in Java?
(23 answers)
Closed 7 years ago.
I'm still newbie to java programming. And can anybody tell me what's wrong with the source code? When I run the code, the conditional assignment always outputs "login failed".
import java.util.Scanner;
public class ProgramBiodataMahasiswa {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String username, password, output;
System.out.print("Enter username : ");
username = input.nextLine();
System.out.print("Enter password : ");
password = input.nextLine();
output = (username=="kesit" && password=="ps123") ? "login successfully" : "login failed" ;
System.out.println(output);
}
}

Use .equals
output = (username.equals("kesit") && password.equals("ps123")) ? "login successfully" : "login failed" ;

With Strings ("quest" and "ps123") you shouldn't be using == to check if they equal. This will compare the pointer and due to the fact that String in Java are immutable, the pointers will always be different. Therefore use
username.equals("kesit") && password.equals("ps123").
That should work!

You can't compare strings in Java using ==. You should use equals method. e.g. username.equals("kesit") && password.equals("ps123")

How would I compare a set of strings? [duplicate]

This question already has answers here:
How do I compare strings in Java?
(23 answers)
Closed 9 years ago.
i have a username and a password string. How can I compare them in Android? This is somewhat what I'm looking for:
if( user== username && pass == password){ then do this }
else if(user[does not equal to]username && pass==password{ toast (invaild username.)}
else if(user==username && pass[does not equal] password{toast(invaild password)}
else{ toast [invaild login]}
I know that's not correct coding but the two "else if" statements is what I'm looking for. The rest is just to give a better understanding of what I'm trying to do.
The username is what's entered into a Edittext same with the Password so they are both String when i .getText.toString right?

To compare the text in strings use equals() e.g. pass.equals(password) rather than == which checks if two strings are the same object.
For "does not equal" you can negate the statement e.g. !pass.equals(password).

Use the equals method for comparing strings.
if( user.equals(username) && pass.equals(password))
{
then do this
}
else if(!user.equals(username) && pass.equals(password)
{
Toast.makeText(this,"invalid username",Toast.LENGTH_SHORT).show();
}
else if(user.equals(username) && !pass.equals(password))
{
Toast.makeText(this,"invalid password",Toast.LENGTH_SHORT).show();
}
else{
Toast.makeText(this,"Invalid login",Toast.LENGTH_SHORT).show();
}

You want to use .equals(..) to compare Strings. Also, to do not logically, you can use !.
//define user, username
//define pass, password
if(user.equals(username) && pass.equals(password)){
//then do this
}
else if(!user.equals(username) && pass.equals(password)){
//toast (invaild username.)
Toast.makeText(getApplicationContext(), "invalid username", Toast.LENGTH_SHORT).show();
}
else if(user.equals(username) && !pass.equals(password)){
//toast(invaild password)
Toast.makeText(getApplicationContext(), "invalid password", Toast.LENGTH_SHORT).show();
}
else{
//toast [invaild login]
Toast.makeText(getApplicationContext(), "invalid login", Toast.LENGTH_SHORT).show();
}
Here are some sources on Toast:
http://www.mkyong.com/android/android-toast-example/
http://developer.android.com/guide/topics/ui/notifiers/toasts.html

You could use pass.equal(password).