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User string input validation and exception error

I'm new in Java programming and I'm trying to create a user input validation to make sure that the user only input one of the three possible strings: Mammals, Reptiles, Birds. But I'm stock on trying to validate and create a loop. So far I have this:
public void validName() {
Scanner typeInput = new Scanner(System.in);
String [] type = {"Mammals", "Reptiles", "Birds"};
System.out.println("Enter Animal Type: ");
String atype = typeInput.next();
try {
if
(!Arrays.asList(type).contains(atype)){
System.out.println("Not a correct animal");
}
}
catch(Exception e){
System.out.println(e+"Plase add the correct Animal Type: (Mammals, Reptile, or Bird");
atype= typeInput.nextLine();}
while (atype.equalsIgnoreCase("Mammals") || atype.equalsIgnoreCase("Reptile") || atype.equalsIgnoreCase("Birds"));
{ System.out.println("Continue to next step");}
}
}
When I run the previous code I get this output:
Please enter First Name
Cris
Please enter Last Name
Cruz
User logged In: Criz Cruz
Welcome to ZooOrganizer!
Enter Animal Type:
Cow
Not a correct animal
Continue to next step
------------------------------------------------------------------------
BUILD SUCCESS
-----------------------------------------------------------------------
I can't get to execute the Catch Exception neither the loop to make the user to input the animal type again.
public void validName() {
Scanner typeInput = new Scanner(System.in);
String [] type = {"Mammals", "Reptiles", "Birds"};
System.out.println("Enter Animal Type: ");
String atype = typeInput.next();
try {
if
(!Arrays.asList(type).contains(atype)){
System.out.println("Not a correct animal");
}
}
catch(Exception e){
System.out.println(e+"Plase add the correct Animal Type: (Mammals, Reptile, or Bird");
atype= typeInput.nextLine();}
while (atype.equalsIgnoreCase("Mammals") || atype.equalsIgnoreCase("Reptile") || atype.equalsIgnoreCase("Birds"));
{ System.out.println("Continue to next step");}
}
}

If you want to think about it, the prompt you have coded is actually rather cruel. It doesn't inform the User of what is expected as input. You may as well display a prompt like:
Hey, enter an Animal Type and if you guess it right
you get two free OH-Henry Bars (yum yum): -->
Be up-front with what is required from the User and if you can, make the entry as simple as possible. If you do then the errors that can be possibly produced by that User is almost completely eliminated, for example:
Enter an Animal Type (Mammals, Reptiles, Birds): -->
Now the User can see what input you're expecting. This however still has issues which your code would need to deal with and take care of such as spelling mistakes, improper letter case, no word entered, etc. In my opinion it's sort of actually a pain in the butt to have to write the word Reptile into something like a Console Application which is why I would avoid those applications, you know :
Enter the full path and file name to your Database located within
the Windows Documents folder: -->
Ya, I don't think so....next app.
When you have multiple items that can be entered then use a Menu System. This way the User can see the choices available and only needs to enter a single letter or number for the desired menu item, for example:
Select an Animal Type (1-3):
1) Mammal
2) Reptiles
3) Birds
4) Quit
Menu Choice: -->
Doing it this way also reduces the amount of code required to carry out validity. Is the entered menu choice an Integer Number, is the entry greater than or equal to 1 and is it less than or equal to 4. If not then tell the User of non-validity and loop again. Here is how you might do this with your current scheme:
String ls = System.lineSeparator();
Scanner typeInput = new Scanner(System.in);
String[] type = {"Mammals", "Reptiles", "Birds"};
String selectedAnimalType = "";
String atype = "";
// Start a prompt WHILE loop...
while (atype.equals("")) {
/* Display a Menu. Doing things this way doesn't leave
the User in the dark as to what is required for input. */
System.out.print("Select an Animal Type (1-3): " + ls
+ "1) Mammal" + ls + "2) Reptiles" + ls
+ "3) Birds" + ls + "4) Quit" + ls
+ "Menu Choice: --> ");
// Get User input...
atype = typeInput.nextLine();
// Is the Input a Valid menu choice?
if (!atype.matches("\\d") || Integer.valueOf(atype) < 1 || Integer.valueOf(atype) > 4) {
/* If it's not a string representation of a Integer numerical value OR
if it's a numerical value less than 1 OR if it's a numerical value
greater than 4 */
System.out.println("Invalid entry! Please try again..." + ls);
atype = ""; // Make atype equal null string ("") to continue WHILE loop
}
// Otherwise, was the menu choice the numerical value 4 to quit?
else if (Integer.valueOf(atype) == 4) {
// Yes, it was...
System.out.println("Quiting... Bye-Bye");
System.exit(0); // Quit (end) Application.
}
}
// Prompt loop successful...continue on with code.
/* Get the proper name for the Animal Type from the 'type' Array
based on the menu choice (numerical value minus 1) so as to get
the desired array index value. */
selectedAnimalType = type[Integer.valueOf(atype) - 1];
/* The condition for the below WHILE loop is redundant since we
would NEVER get this far unless a menu choice for either Mammal,
Reptiles, or Birds, was made, so don't bother using it. Do something
similar as to what was done in the first prompt loop above. */
while (atype.equalsIgnoreCase("Mammals") || atype.equalsIgnoreCase("Reptile") || atype.equalsIgnoreCase("Birds")) {
System.out.println("Continue to next step");
// ........................................
}

You should use a Do...While loop in this case:
public void validName() {
Scanner typeInput = new Scanner(System.in);
String [] type = {"Mammals", "Reptiles", "Birds"};
do {
System.out.println("Enter Animal Type: ");
String atype = typeInput.next();
try {
if
(!Arrays.asList(type).contains(atype)){
System.out.println("Not a correct animal");
System.out.println("Continue to next step");}
}
}
catch(Exception e){
System.out.println(e+"Plase add the correct Animal Type: (Mammals, Reptile, or Bird");
atype= typeInput.nextLine();}
} while (atype.equalsIgnoreCase("Mammals") || atype.equalsIgnoreCase("Reptile") || atype.equalsIgnoreCase("Birds"));
}

Exiting While Loop After User Enters Value in String (Java)

Hello fellow StackOverflowers, I hope all of your days are going well.
I'm relatively new to Java programming and have found myself in a bit of pickle.
What I'm attempting to do is;
Input Validation in Java - I want to make sure that the JOptionPane.showInput pane continues to re-appear (using a while loop) until the user has entered a value which is captured in the "this.accountName" String and;
From there once the user has entered something in the JOptionPane.showInput pane I want to exit the loop and proceed to the other methods I have inside my OO program.
Unfortunately my while loop below exits after the first instance and doesn't continue in my code example below;
public String getAccountName() {
this.accountName = JOptionPane.showInputDialog(null, "Please enter a nick name for your new account (e.g. Savings Account)");
if (this.accountName!= null) {
while (this.accountName != null) {
this.accountName = JOptionPane.showInputDialog(null, "Error! Please enter a valid name for your new account");
if (this.accountName.contains("")){return this.accountName;
}
}
}
return this.accountName;
}
What would be the best way to go about fixing this?
I appreciate your help in advance!

Use StringUtils.isBlank method (https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html) to check accountName value:
this.accountName = JOptionPane.showInputDialog(null, "Please enter a nick name for your new account (e.g. Savings Account)");
while (StringUtils.isBlank(this.accountName)) {
this.accountName = JOptionPane.showInputDialog(null, "Error! Please enter a valid name for your new account");
}
return this.accountName;

When user presses "enter" key or space enter then error message pops up

I would like to print an error message when the user presses enter or space enter instead of a string. I have tried isEquals("") and isEmpty() but haven't found anything that works yet.
Here's my code:
import java.util.Scanner;
public class check{
public static void main(String args[]){
System.out.println("Enter a number: ");
Scanner keyboard = new Scanner(System.in);
String input = keyboard.next();
if(input.equals("")){
System.out.println("Empty");
} else {
System.out.println("number inputed");
}
}
}

One way to do this, change keyboard.next() to keyboard.nextLine(), use trim() to remove unnecessary spaces, check with isEmpty().
String input = keyboard.nextLine().trim();
if (input.isEmpty()) {
// error message
} else {
// good to go
}

import java.util.Scanner;
public class check{
public static void main(String args[]){
System.out.println("Enter a number: ");
Scanner keyboard = new Scanner(System.in);
String input = keyboard.nextLine();
if(input.trim().equals("")){
System.out.println("Empty");
} else {
System.out.println("number inputed");
}
}
}

Strangely, I don't get an error when running your code. However, I noticed that your code simply doesn't react to an empty input (just pressing enter). If you want to check for that, you can use keyboard.nextLine().
Judging by the rest of your code, it seems like you want the user to input only a number. An easy way to check if the user entered an integer if you're using Scanner is keyboard.hasNextInt().
Meaning you can do something like this:
if(keyboard.hasNextInt()) {
int yourNumber = keyboard.nextInt();
System.out.println("Your number is: " + your Number);
}
else {
System.out.println("Please enter a valid integer");
}

To check whether the string input is empty, you can use the String.isEmpty() method. Look below:
String input = keyboard.nextLine();
if(!input.isEmpty()) {
//the input is not empty!
}
else {
//the input is empty!
}
Note, however, that since you want to receive numbers as inputs you should not retrieve them as strings. Below is an example where the program retrieves a double from the user. Scanner provides many methods to validate the user's input. In this case, I'm using hasNextDouble() to check whether the input is a number.
Scanner scanner = new Scanner(System.in);
System.out.println("Enter a number:");
while(!scanner.hasNextDouble()) {
System.out.println("That's not a number!");
scanner.next();
}
double numberInput = scanner.nextDouble();
System.out.println("The entered number was " + numberInput);

I made a sample program similar to yours and used nextLine() instead of next(). When user enters space and clicks enter he will print "space" else "a number".

Strange output when I read from scanner

I'm trying to create a videoStore with the basic CRUD operation. For creating each movie I need to read the title, the year and the gender as below:
System.out.print("name: ");
name = in.nextLine();
System.out.print("year: ");
year = in.nextInt();
in.nextLine();
System.out.print("gender: ");
gender = in.next();
When I enter the addMovie option, I get this print on the console
(name: year:)
Can someone explain to me why it happens as above?
Here is the rest of the method:
static ArrayList<Movie> movies = new ArrayList<Movie>();
static Scanner in = new Scanner(System.in);
public static void InserirFilme() {
String name;
int year;
String gender;
boolean existe = false;
System.out.print("name: ");
name = in.nextLine();
System.out.print("year: ");
year = in.nextInt();
in.nextLine();
System.out.print("gender: ");
gender = in.next();
Movie movie = new Movie(name, year, gender);
for(Movie m: movies)
{
if(movie == m)
{
existe = true;
}
}
if(!existe)
{
movies.add(movie);
}
else
{
System.out.println("the movie already exists in the videoStore");
}
}

Calling next does not remove the line break, which means the next time you call InserirFilme the call to read the name can complete immediately. Use nextLine.
System.out.print("gender: ");
gender = in.nextLine();
(You probably mean "genre" instead of "gender" though)
Also, as mentioned in the comments, this check will never succeed:
if(movie == f)

You run this method in loop (right?)
The first call reads input correctly, but it leaves the linebreak in System.in after the last in.next().
On next call the name: is printed, then scanner reads an empty string from System.in because the linebreak already exists here.
And after thet the year: is printed on the same line because no new linebreaks are entered.
So you just have to insert another in.nextLine() after reading gender (or genre :) )
Or use nextLine() for read genre instead of next(), because genre might have more than one word.
But there are some disadvantages with using fake nextLine() to 'eat' linebreak - there might be another text which you doesn't process. It's a bad practice - to loose the data user entered.
It is better to read all the data from line, then validate/parse it, check isn't there some extra data, and if the data is invalid show notification and let him try to enter the right value.
Here are some examples how to deal with user input manually - https://stackoverflow.com/a/3059367/1916536. This is helpful to teach yourself.
Try to generalize user input operations:
name = validatedReader.readPhrase("name: ");
year = validatedReader.readNumber("year: ");
genre = validatedReader.readWord("genre: ");
where ValidatedReader is a custom wrapper for Scanner which could use your own validation rules, and could gently re-ask user after a wrong input.
It could also validate dates, phone numbers, emails, url's or so
For production purposes, it is better to use validation frameworks with configurable validation rules. There are a lot of validation frameworks for different purposes - Web, UI, REST etc...

when i enter the addMovie option, i get this print on the console (name: year:) can someone explain me why it happens i already searched a lot and i cant understand why :S
The way i understood your question is that you are getting the output (name: year: ) in a line and want it in seperate lines? In that case you simply can use System.out.println(String); instead of System.out.print(String). On the other hand you can also use "\n" whenever you want a linebreak within a String. Hope i could help you :).
Edit: If this was not an answer to your question, feel free to tell me and clarify your question :)

For String name you are using in.nextLine(); i.e the data entered on the entire line will be added to name string.
After "name: " is displayed, enter some text and press enter key, so that the year and gender fields will get correct values.
The code written is correct but you are not giving appropriate input through the scanner.
I recommend to use
String name = in.next();//instead of String name = in.nextLine();

You may instantiate Scanner Class differently for String and Integer type input. It works for me :)
Example:
static Scanner in1 = new Scanner(System.in);
static Scanner in2 = new Scanner(System.in);
Please use nextLine() for 'name' and 'gender'. It may contain more than one word. Let me know if it works.
Example:
System.out.print("name: ");
name = in1.nextLine();
System.out.print("year: ");
year = in2.nextInt();
System.out.print("gender: ");
gender = in1.nextLine();

Repeating error message inside a while loop [duplicate]

This question already has answers here:
Loop user input until conditions met
(3 answers)
Closed 7 years ago.
I'm currently working my way through a Udemy Java course and am practicing what i have learnt thus far.
I have the following simple program which i am planning on using to get the user to input his name.
import java.util.Scanner;
public class Adventure {
public static final int menuStars = 65;
private static Scanner input = new Scanner(System.in);
public static void main(String[] args) {
String firstName = "";
String lastName = "";
boolean validName = false;
while(!validName){
//Entering first name
System.out.println("Please enter your first name.");
try {
firstName = input.nextLine();
if(firstName.length() == 0){
throw new Exception("Please enter a first name of at least 1 character.");
}else{
//Entering last name
System.out.println("Please enter your last name.");
lastName = input.nextLine();
if(lastName.length() == 0){
throw new Exception("Please enter a last name of at least 1 character");
}else{
System.out.println("You have entered " + firstName +" " + lastName);
}
}
} catch (Exception e) {
System.out.println(e.getMessage());
continue;
}
//Used to terminate loop when both first & last names are valid
validName = true;
}
}
}
I want to make the program repeat the error message when the user inputs a blank name instead of restarting the entire program from the beginning.
E.g When the user enters a blank first name, i want the program to keep repeating "Please enter a first name of at least 1 character" and when the user enters a blank last name, for it to keep repeating "Please enter a last name of at least 1 character" until the user enters a valid name.
However, currently when the user enters a blank first name or last name, my program will repeat itself from the very beginning instead of repeating just the error message.
How would i go about making the program repeat just the error message?

Use a boolean variable that stores true when "Please enter your first name." is printed. Check before printing this string each time if this variable is false or not. Also, initialize it to false before the loop. Same idea goes for last name.
if(!printed)
{
System.out.println("Please enter your first name.");
printed=true;
}

havent tested that but i am guessing it can be like that, with out try/catch though, it just makes no sense to me using it in the way you have it on your code
String firstName = "";
String lastName = "";
System.out.println("Please enter your first name.");
firstName = input.nextLine();
while(firstName.length<1){
System.out.println("Please enter a first name of at least 1 character.");
firstName = input.nextLine();
}
lastName=input.nextLine();
while(firstName.length<1){
System.out.println("Please enter a last name of at least 1 character.");
lastName = input.nextLine();
}
System.out.println("You have entered " + firstName +" " + lastName);
Edit, some basic info about exceptions
try catch is used when something unexpected happens and you try to find a way round it. for example if an array of 10 positions is expected at some point and a smaller array (lets say 4 positions) is being used. Then this would cause an exception causing the program to terminate with no further information.
With try catch you can check what the problem is, and try to either inform the user to do something(if they can) or close the program in a better way, using System.exit() for example and saving all the work that was done till that point
An other example is that if you ask for 2 numbers to do an addition. if the user enters letters instead of number the int sum=numbA+numbB; would throw and exception. This of course could be handled using an if. but even better would be something like this

A whitespace is actually considered a character, so the check of (length == 0) doesn't work for your purposes.
Although the following code below is incomplete (ex: handles the potentially undesirable case of firstname=" foo", (see function .contains()), it does what the original post asks - when the user enters a blank first/last name, it keeps repeating "Please enter a first/last name of at least 1 character" until the user enters a valid first/last name.
import java.util.Scanner;
public class Adventure {
public static final int menuStars = 65;
private static Scanner input = new Scanner(System.in);
public static void main(String[] args) {
String firstName = "";
String lastName = "";
boolean firstNameLegal = false;
boolean lastNameLegal = false;
// Entering first name
while (!firstNameLegal) {
System.out.println("Please enter your first name.");
firstName = input.nextLine();
if (!firstName.equals(" "))
firstNameLegal = true;
else
System.out.println("Please enter a first name of at least 1 character.");
}
// Entering last name
while(!lastNameLegal){
System.out.println("Please enter your last name.");
lastName = input.nextLine();
if(!lastName.equals(" "))
lastNameLegal = true;
else
System.out.println("Please enter a last name of at least 1 character.");
}
System.out.println("You have entered " + firstName +" " + lastName);
}
}