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Java. Scanner requests an additional line but does not print it

just entered this community and this is my first question here, so please bear with a noob. I created two classes, first is Student, a basic one with fields, constructor and getters. The second one has the main method, a LinkedList, a multiple-entry Scanner (for...) and two simple methods.
My problem is that despite the fact that the For loop has maximum index 1 (x = 0; x < 2), the Scanner expects a third row input and an enter but does not print the third line. I add the two classes, maybe I made a mistake and I would appreciate your help. Thank you in advance.
public class Student {
private String name;
private String surname;
private int firstMark;
private int secondMark;
private int finalExamMark;
public Student(String name, String surname, int firstMark, int secondMark, int finalExamMark) {
this.name = name;
this.surname = surname;
this.firstMark = firstMark;
this.secondMark = secondMark;
this.finalExamMark = finalExamMark;
}
public String getName() {
return name;
}
public String getSurname() {
return surname;
}
public int getFirstMark() {
return firstMark;
}
public int getSecondMark() {
return secondMark;
}
public int getFinalExamMark() {
return finalExamMark;
}
#Override
public String toString (){
return this.name + " " + this.surname + " got " + this.firstMark + " at English, " + this.secondMark + " at Math and " + this.finalExamMark + " at the final exam.";
}
}
public class StudentMain {
static LinkedList<Student> courseAttend = new LinkedList<>();
static Scanner scanner = new Scanner(System.in);
public static void main(String[] args) {
addStudent();
printList(courseAttend);
}
private static void addStudent() {
for (int x = 0; x < 2; x++) {
String s1 = scanner.nextLine();
String[] split = s1.split("\\s");
courseAttend.add(new Student(split[0], split[1], Integer.parseInt(split[2]), Integer.parseInt(split[3]), Integer.parseInt(split[4])));
scanner.nextLine();
}
scanner.close();
}
private static void printList(LinkedList<Student> lista) {
for (Student elem : lista) {
System.out.println(elem);
}
}
}
For example, if I input (without quotes)
"Young John 9 9 9"
"Johnson Anne 8 8 8" and I press enter, the cursor moves to next line and waits another input. Only after that third line and the final enter, the message is displayed but the third line is not shown.

courseAttend should be a List<Student> courseAttend = new ...List<>(); like your methode argument printList(List<Student> students) because both could be also a ArrayList and it is the normal way to in implement variables if they have not to be sepciefied, like in your case.
The loop has two nextLine() but you ignore the second one so you are creating a student and waiting of the next input and not saving the input
When a User has to enter multiple arguments for any given prompt, you can expect to have typos. Your prompt expects the User to enter 5 arguments and they are not even from the same typ on a single line delimited with a whitespace. What if the user accidentally give you an ivalid input like a integer as name or a String as mark.
public class StudentMain {
static List<Student> courseAttend = new LinkedList<>();
static Scanner scanner = new Scanner(System.in);
public static void main(String[] args) {
for (int x = 0; x < 2; x++) {
courseAttend.add(createStudent());
}
scanner.close();
printList(courseAttend);
}
private static Student createStudent(){
System.out.print("name: ");
String name = scanner.nextLine();
System.out.print("surname: ");
String surname = scanner.nextLine();
System.out.print("first mark: ");
int firstMark = scanner.nextInt();
System.out.print("second mark: ");
int secondMark = scanner.nextInt();
System.out.print("final exam mark: ");
int finalExamMark = scanner.nextInt();
return new Student(name, surname, firstMark, secondMark ,finalExamMark);
}
private static void printList(List<Student> students) {
for (Student elem : students) {
System.out.println(elem);
}
}
}

while loop with store value for next while loop in java

I'm a beginner in Java. I have an assignment that require me to take 3 input from user, then output the 3 at the same time.
here is my code. i have only get 1 output.
suppose look like this:
anyone could help, thx!
here is my code
Scanner sc = new Scanner(System.in);
int i = 0;
String classname = " ";
String rating = " ";
int plus = 0;
while(i < 3){
System.out.print("What class are you rating? ");
classname = sc.nextLine();
System.out.print("How many plus signs does " + classname +" get? ");
rating = sc.nextLine();
plus = Integer.parseInt(rating);
i++;
}
System.out.print(classname + ": ");
while (plus > 0){
System.out.print("+");
plus --;
}
System.out.println();

The very first thing I would do is create a Course POJO (Plain Old Java Object). It should have two fields, name and rating. And I would implement the display logic with a toString in that Course POJO. Like,
public class Course {
private String name;
private int rating;
public Course(String name, int rating) {
this.name = name;
this.rating = rating;
}
public String toString() {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < rating; i++) {
sb.append("+");
}
return String.format("%s: %s", name, sb);
}
}
Then your main method simply involves filling a single array of three Course instances in one loop, and displaying them in a second loop. Like,
Scanner sc = new Scanner(System.in);
Course[] courses = new Course[3];
int i = 0;
while (i < courses.length) {
System.out.print("What class are you rating? ");
String className = sc.nextLine();
System.out.printf("How many plus signs does %s get? ", className);
int classRating = Integer.parseInt(sc.nextLine());
courses[i] = new Course(className, classRating);
i++;
}
i = 0;
while (i < courses.length) {
System.out.println(courses[i]);
i++;
}

You overwrite your variables classname and rating in each loop. You need to store each iteration in a field of an array.
Scanner sc = new Scanner(System.in);
int i = 0;
String[] classname = new String[3]; //create array
String rating = " "; //rating can be overwritten, it is not needed after the loop
int[] plus = new int[3];
while(i < 3){
System.out.print("What class are you rating? ");
classname[i] = sc.nextLine(); //name[index] to read/write fields of an array
//index starts at 0
System.out.print("How many plus signs does " + classname +" get? ");
rating = sc.nextLine();
plus[i] = Integer.parseInt(rating);
i++;
}
for(i = 0;i<3;i++){ //iterate over all elements in the array
System.out.print(classname[i] + ": ");
while (plus[i] > 0){
System.out.print("+");
plus[i] --;
}
System.out.println();
}

Sorting Arrays In Java soicanpost

my question is how would I sort the arrayofnames and arrayofdownloads so they're in ascending order and each name matches with it corresponding number of downloads. i've been trying for 4 hours and i can't seem to wrap my head around it
thanks
import java.util.*;
import java.util.stream.*;
public class short6
{
public static void main(String[] args)
{
String[] arrayofnames = new String[4];
int[] arrayofdownloads = new int[4];
printmessage(arrayofnames, arrayofdownloads);
details(arrayofnames, arrayofdownloads);
System.exit(0);
}
public static void printmessage(String[] arrayofnames, int[] arrayofdownloads)
{
Scanner scanner = new Scanner(System.in);
int totalDownloads = 0;
for (int i = 0; i < arrayofnames.length; i++)
{
System.out.println("What is track " + (i + 1));
arrayofnames[i] = scanner.nextLine();
System.out.println("How many thousands of times has it been downloaded? ");
arrayofdownloads[i] = Integer.parseInt(scanner.nextLine());
}
Arrays.sort(arrayofnames);
Arrays.sort(arrayofdownloads);
System.out.println("The track downloaded the most is " + arrayofdownloads[0]+".");
}
public static void details(String[] arrayofnames, int[] arrayofdownloads)
{
int totaldownloads = IntStream.of(arrayofdownloads).sum();
System.out.println("The track downloaded the most is " + arrayofdownloads[0]+".");
System.out.println("The total number of downloads of these 4 tracks was " + totaldownloads * 1000 +".");
System.out.println("\nThe details of the downloads are");
for (int i = 1; i < arrayofnames.length; i++)
{
System.out.println(arrayofnames[i]);
System.out.println((arrayofdownloads[i]));
}
}
}

I'd start creating a Song (e.g.) class that contains both the song name, and the number of downloads:
public class Song {
private String name;
private int downloads;
public Song(String name, int downloads) {
this.name = name;
this.downloads = downloads;
}
public String getName() {
return this.name;
}
public int getDownloads() {
return this.downloads;
}
}
And then, create an array of songs:
Song[] arrayOfSongs = new Song[4];
And load it from the input:
arrayOfSongs[i] = new Song(scanner.nextLine(), Integer.parseInt(scanner.nextLine()));
Now you just need to sort it using a comparator:
Arrays.sort(arrayOfSongs, new Comparator<Song> () {
public int compare(Song o1, Song o2) {
// Sorting by name
return o1.getName().compareTo(o2.getName());
}
});
Or, as #Benoit has said in the comments, it would be even easier this way (Java 8 or up):
Arrays.sort(arrayOfSongs, Comparator.comparing(Song::getName));
And your done, just printing the objects (a toString method can be helpful here) you have the information sorted.
Edit: to read the input writing the questions, you just need to store the values in variables e.g.
System.out.println("What is track " + (i + 1));
String songName = scanner.nextLine();
System.out.println("How many thousands of times has it been downloaded? ");
int songDownloads = Integer.parseInt(scanner.nextLine());
arrayOfSongs[i] = new Song(songName, songDownloads);
Or you can just implement setter methods in the Song class and create a constructor with no parameters, so you can set the values as you are reading them.

thanks for the reply, so I've figured that i can use a for loop to ask the questions for song name and number of downloads. what im finding hard is putting their response in each array from 1-4 and saving dong name in the correct field of the song record and same for number of downloads?
public static void printmessage(song[] arrayOfSongs)
{
Scanner scanner = new Scanner(System.in);
int totalDownloads = 0;
for (int i = 0; i < arrayOfSongs.length; i++)
{
System.out.println("What is track " + (i + 1));
// store in array x name field
System.out.println("How many downloads does this track have? ");
//store in array x downloads field
}

Why is the LinkedList being printed as blank?

Can someone tell me why my baggage won't print?
For passenger name I enter, say, John.
For country code I enter: BI
For flight number I enter: 095
For number of baggage I can enter any amount.
Let's say I enter: John, BI, 095, 3.
This is what I get: [John with baggage(s) [, , ]] when I should be getting
[John with baggage(s) [BI0950, BI0951, BI0952]]
Sorry if the code is quite messy.
It's amended. Thanks guys.
import java.util.*;
public class baggageSys{
public static String getUser_command(){
Scanner keyboard = new Scanner(System.in);
System.out.print("Enter command B-baggage, n-next, q-quit");
String s = keyboard.nextLine();
return s;
}
public static String getUser_flight(){
Scanner keyboard = new Scanner(System.in);
System.out.println("Please enter the flight number");
String s = keyboard.nextLine();
return s;
}
public static String getPassenger(){
Scanner keyboard = new Scanner(System.in);
System.out.println("Please enter passenger name");
String s = keyboard.nextLine();
return s;
}
public static String getUser_country(){
Scanner keyboard = new Scanner(System.in);
System.out.println("Please enter the country code");
String s = keyboard.nextLine();
return s;
}
public static int getUser_number(){
Scanner keyboard = new Scanner(System.in);
System.out.println("Please enter number of baggage");
int s = keyboard.nextInt();
return s;
}
public static String next(ListIterator<Passenger> passenger){
String k = "";
passenger.next();
return k;
}
public static String makeBaggage(String country, String flight, int num){
return country + flight + num;
}
public static void main(String args[]) {
LinkedList<Passenger> passenger = new LinkedList<Passenger>();
ListIterator<Passenger> iterator = passenger.listIterator();
LinkedList<String> baggage = new LinkedList<String>();
String command = "";
while (!command.equals("q")){
command = getUser_command();
if(command.equals("B") || command.equals("b")){
String p = "";
p = getPassenger();
passenger.add(new Passenger(p));
// command = getUser_command();
String country = "";
country = getUser_country();
String flight = "";
flight = getUser_flight();
int amount = 0;
amount = getUser_number();
String[] bg = new String[amount];
for(int i = 0; i < amount; i++){
bg[i] = makeBaggage(country, flight, i);
baggage.add(bg[i]);
System.out.println(bg[i]);
passenger.getLast().setBaggages(baggage);
}
System.out.println(passenger);
} else if(command.equals("n")){
next(iterator);
}
else
System.out.println("Enter 'q' to end the program");
}
}
public static class Passenger {
String passengers;
List<String> baggage;
public Passenger(String passengers) {
this.passengers = passengers;
baggage = Collections.emptyList();
}
public void setBaggages(List<String> baggage) {
this.baggage = baggage;
}
#Override
public String toString() {
return passengers + " with baggage(s) " + baggage;
}
}
}

You're not returning anything in your makeBaggage method, as you can see after the loop it returns the x variable which is not either set inside the loop, in this case your loop is useless.
public static String makeBaggage(String country, String flight, int num){
String x = "";
for(int i = 0; i < num; i++){
String[] bgs = new String[num];
bgs[i] = country + flight + i;
// System.out.println(bgs[i]);
}
return x;
}
I think this is the one you're looking for:
public static String makeBaggage(String country, String flight, int num){
return country + flight + num;
}
For this specific line in your code:
for(int i = 0; i < amount; i++){
String[] bg = new String[amount];
bg[i] = makeBaggage(country, flight, amount);
baggage.add(bg[i]);
System.out.println(bg[i]);
...
Move the String[] bg = new String[amount]; declaration outside of the for loop and instead of supplying the amount in the makeBaggage method, use the loop counter instead as follows: bg[i] = makeBaggage(country, flight, i);
String[] bg = new String[amount];
for(int i = 0; i < amount; i++){
bg[i] = makeBaggage(country, flight, i);
baggage.add(bg[i]);
System.out.println(bg[i])
..
I think that should do it. Also, your code could be greatly improved, and that would be your tasks.

Java: creating an array inside of an object class?

I'm attempting to save an x amount of integers inside of an object class. I'm trying it via an array but am not sure if this is possible and as of now eclipse is giving me two errors. One asking me to insert an Assignment operator inside of my Gerbil() class and another saying that I can't make a static reference to to the non-static field food. The result I'm looking for is food 1 = first input; food 2 = second input; until it hits the total amount of food.
Here's my code so far:
import java.util.Scanner;
public class Gerbil {
public String name;
public String id;
public String bite;
public String escape;
public int[] food;
public Gerbil() {
this.name = "";
this.id = "";
this.bite = "";
this.escape = "";
this.food[]; // I'm not sure what I should put here. This is where I want to store
} // the different integers I get from the for loop based on the
// total number of foods entered. So if totalFoods is 3, there should
// be 3 integers saved inside of the object class based on what's typed
// inside of the for-loop. Or if totalFoods = 5, then 5 integers.
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
System.out.println("How many foods?");
int totalFood = keyboard.nextInt();
System.out.println("How many gerbils in the lab?");
int numberOfGerbils = keyboard.nextInt();
Gerbil[] GerbilArray = new Gerbil[numberOfGerbils];
for(int i = 0; i <= numberOfGerbils; i++){
GerbilArray[i] = new Gerbil();
System.out.print("Lab ID:");
String id = keyboard.next();
System.out.print("Gerbil Nickname:");
String name = keyboard.next();
System.out.print("Bite?");
String bite = keyboard.next();
System.out.print("Escapes?");
String city = keyboard.nextLine();
for (int j = 0; j < totalFood; j++) {
System.out.println("How many of food " + (j+1) + "do you eat?:");
food[j] = keyboard.nextInt();
}
}
}
}

You need to pass the number of food in the Gerbil constructor :
public Gerbil(int totalFood) {
this.name = "";
this.id = "";
this.bite = "";
this.escape = "";
this.food[] = new int[totalFood];
}
And then in the loop will look like this :
for(int i = 0; i <= numberOfGerbils; i++){
GerbilArray[i] = new Gerbil(totalOfFood);
System.out.print("Lab ID:");
String id = keyboard.next();
System.out.print("Gerbil Nickname:");
String name = keyboard.next();
System.out.print("Bite?");
String bite = keyboard.next();
System.out.print("Escapes?");
String city = keyboard.nextLine();
for (int j = 0; j < totalFood; j++) {
System.out.println("How many of food " + (j+1) + "do you eat?:");
GerbilArray[i].food[j] = keyboard.nextInt();
}
}
Or something like that should do it.