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Print a specific cell from a string array

I've created a class that includes people data named "Datiutente" and an object based on that class named "du". Every person has a name and a surname (with the set/get methods).
I want to create a system that can provide the user information on a specific person based on the position which they are stored in the array.
I tried using a variable named vd to ask the user which person wanted to visualize based on the position that a person gained in the array (inserted in the for cycle), but when I try to print with vd it just prints "Name: null". Same if I change "vd" to "1". It always prints "Null".
(Yes, I tested this when I already inserted some data.)
Here's the full code:
package appartamento;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class Appartamento {
public static void main(String[] args) throws IOException {
InputStreamReader input = new InputStreamReader(System.in);
BufferedReader keyb = new BufferedReader(input);
boolean attiva = true;
do {
System.out.println("what do you want to do?");
System.out.println("1 - check for a person");
System.out.println("2 - Add person");
int choice = Integer.parseInt(keyb.readLine());
Datiutente du[] = new Datiutente[10];
if (choice == 2){
System.out.println("How many people?");
int hm = Integer.parseInt(keyb.readLine());
for (int i=0;i<hm;i++){
du[i] = new Datiutente();
System.out.println("insert name:");
du[i].setName(keyb.readLine());
System.out.println("insert surname");
du[i].setSurname(keyb.readLine());
}
}
if (choice == 1){
System.out.println("which person are you searching?");
int vd = Integer.parseInt(keyb.readLine());
System.out.println("position: " + i);
System.out.println("Name: "+ du[i]);
System.out.println("Surname: " + du[i]);
}
} while (attiva = true);
}
}
and the class "Datiutente":
package appartamento;
public class Datiutente {
private String name;
private String surname;
private String codfis;
public void setName(String name){
this.name = name;
}
public String getName(){
return name;
}
public void setSurname(String surname){
this.surname = surname;
}
public String getSurname(){
return surname;
}
}

In every iteration you define the Datiutente du[] = new Datiutente[10];, so du is reset to {null,...,null} and the data saved in the previous iteration are replaced;
Try to define the array before the loop statement.

I found a way here:
You need to insert values on object creation, you can also use hashmaps
hashmap will benefit you more I think.
Code sample to fix your stuff.
class GFG {
public static void main(String args[]){
// Declaring an array of student
Student[] arr;
// Allocating memory for 2 objects
// of type student
arr = new Student[2];
// Initializing the first element
// of the array
arr[0] = new Student(1701289270, "Satyabrata");
// Initializing the second element
// of the array
arr[1] = new Student(1701289219, "Omm Prasad");
// Displaying the student data
System.out.println(
"Student data in student arr 0: ");
arr[0].display();
System.out.println(
"Student data in student arr 1: ");
arr[1].display();
}
}
class Student {
public int id;
public String name;
// Student class constructor
Student(int id, String name)
{
this.id = id;
this.name = name;
}
// display() method to display
// the student data
public void display()
{
System.out.println("Student id is: " + id + " "
+ "and Student name is: "
+ name);
System.out.println();
}
}

How to make private hashmap in one class visible to other class [closed]

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Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 1 year ago.
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So everything works great in my program, but I read that making variable not private in class is a big mistake, because it can make problems with others part of big program.
Well I tried making HashMap airplane and flight private but I get error that "The field Airplane.airplane is not visible",which is of course true.
But how do I then make it visible in interface class?
Thanks in advance, I'm still learning and I got to this part in course.
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner imeskanera = new Scanner(System.in);
Airplane airplane = new Airplane();
flight flight = new flight();
interface_aerodrom ui = new interface_aerodrom(imeskanera,airplane,flight);
ui.start();
}
}
/ Airplane class
import java.util.HashMap;
public class Airplane {
HashMap<String,Integer>airplane;
private String id;
private int capacity;
public Airplane() {
this.airplane = new HashMap<String,Integer>();
}
public void add(String id, int capacity) {
this.id = id;
this.capacity = capacity;
this.airplane.put(id, capacity);
}
public String id() {
return this.id;
}
public int capacity() {
return this.capacity;
}
public String airplaneinfo() {
return this.id + "( " + this.capacity + " )";
}
}
/interface class
import java.util.Scanner;
public class interface_aerodrom {
private Scanner imeskanera;
private Airplane airplane;
private flight flight;
public interface_aerodrom(Scanner scanner, Airplane airplane,flight flight) {
this.imeskanera = scanner;
this.airplane = airplane;
this.flight = flight;
}
public void start() {
System.out.println("Airport panel\r\n"
+ "--------------------");
System.out.println();
while(true) {
System.out.println("Choose operation:\r\n"
+ "[1] Add airplane\r\n"
+ "[2] Add flight\r\n"
+ "[x] Exit");
String input = this.imeskanera.nextLine();
input = input.toLowerCase();
input = input.trim();
if(input.equals("x")) {
flight_service();
break;
}
else if(input.equals("1")) {
addairplane();
}
else if(input.equals("2")){
addflight();
}
}
}
public void flight_service() {
System.out.println("Flight service\r\n"
+ "------------");
while(true) {
System.out.println("Choose operation:\r\n"
+ "[1] Print planes\r\n"
+ "[2] Print flights\r\n"
+ "[3] Print plane info\r\n"
+ "[x] Quit");
String input = this.imeskanera.nextLine();
input = input.toLowerCase();
input = input.trim();
if(input.equals("quit")){
break;
}
else if(input.equals("1")) {
for(String name : this.airplane.airplane.keySet()) {
int numberofseats = this.airplane.airplane.get(name);
String list = name + "( " + numberofseats + " )";
System.out.println(list);
}
}
else if(input.equals("2")){
for(String name : this.flight.flight.keySet()) {
String value = this.flight.flight.get(name);
String list = name + value;
System.out.println(list);
}
}
else if(input.equals("3")) {
System.out.println("Give plane ID: ");
String planeid = this.imeskanera.nextLine();
if(airplanecontains(planeid)) {
int numberofseats = this.airplane.airplane.get(planeid);
System.out.println(planeid + "( " + numberofseats + " )" );
} else {
System.out.println("That plane is not in our database");
}
}
}
}
public void addairplane() {
System.out.println("Give plane ID: ");
String ID = this.imeskanera.nextLine();
System.out.println("Give plane capacity: ");
int capacity = Integer.parseInt(this.imeskanera.nextLine());
this.airplane.add(ID, capacity);
}
public boolean airplanecontains(String ID) {
if(this.airplane.airplane.containsKey(ID)) {
return true;
}else {
return false;
}
}
public void addflight() {
System.out.println("Give plane ID: ");
String ID = this.imeskanera.nextLine();
if(airplanecontains(ID)) {
System.out.println("Give departure airport code: ");
String departure = this.imeskanera.nextLine();
System.out.println("Give destination airport code: ");
String destination = this.imeskanera.nextLine();
int seats = this.airplane.airplane.get(ID);
this.flight.flight.put(ID + " ( " + seats + " ) ",departure + "-" + destination);
}
else {
System.out.println("This plane is not in our database");
}
}
}
/ flight class
import java.util.HashMap;
public class flight {
HashMap<String,String>flight;
public flight() {
this.flight = new HashMap<String,String>();
}
public void add(String departure, String destination) {
this.flight.put(departure, destination);
}
}

Making a field private does not necessarily mean you can't share it. You can use a getter to return the HashMap.
private Map<String,Integer>airplane = new HashMap<>();
public Map<String,Integer> getAirPlaneMap() {
return airplane;
}
The reason being is that this hides implementation details and allows for future changes without affecting users of the class. Users don't need to know where the map comes from within your class. You could have retrieved it from some where yourself and the user wouldn't know.
You may also want to ensure a user can't change it. So you could do the following:
public Map<String,Integer> getAirPlaneMap() {
return Collections.unModifiableMap(airplane);
}
The above will prevent the user from adding or deleting map elements. But it won't prevent them from changing a retrieved object from the map unless that object is also immutable.
In general, setter and getters are the best way to allow users to set and retrieve values. And it is usually a good idea to make defensive copies of mutable items that they are retrieving to ensure that the retrieved values are consistent for all users during execution of the program.

Need help making ArrayList

I am trying to create an ArrayList using at least six Person objects that will contain user inputted name and age resulting in information being printed out in alphabetical order.
Array list that contains person:
import java.util.Scanner;
import java.util.List;
import java.util.ArrayList;
public class Categorization
{
public static Scanner input = new Scanner(System.in);
public static void main(String[] args)
{
List<Person> people = new ArrayList<Person>();
System.out.println("Please enter a name " + name); // Can't return values
String nameEntry = input.toString();
System.out.println("Please enter an age " + age);
int ageEntry = input.nextInt();
}
}
I am unfamiliar with creating classes and feel like this is where most of my errors occur.
class Person
{
private String name;
private int age;
public Person(String name, int age)
{
this.name = name;
this.age = age;
}
Tried to return name and age but they are not going back to the Public Class
public String getName()
{
return name;
}
public int getAge()
{
return age;
}
}
}

You can try this:
public class Categorization {
public static Scanner input = new Scanner(System.in);
public static void main(String[] args) {
List<Person> people = new ArrayList<Person>();
for(int i=1; i<=6; i++) {
System.out.print("Please enter name for person " + i + " : ");
String nameEntry = input.next();
System.out.print("Please enter an age for person " + i + " : ");
int ageEntry = input.nextInt();
Person obj = new Person(nameEntry, ageEntry);
people.add(obj);
}
System.out.println("List of entries you entered: ");
for(Person obj: people) {
System.out.println("Name: " + obj.getName() + " " + "Age: " + obj.getAge());
}
}
}
Output:
You need to create a Person object using new keyword to store respective values and then finally add it to the people list.

Java - Using variable from another class as method argument

In my Main class I have this piece of code:
UUID uniqueID;
public void createEmployee(){
uniqueID = UUID.randomUUID();
// ...
}
In my class Corporation there's a method called promoteEmployee, which should receive the uniqueID as parameter. Is that possible, and when yes, how?
public void promoteEmployee(uniqueID){
// it doesn't recognize uniqueID as argument
}
I also have the method sortEmployees, which sorts the ArrayList alphabetically, and if two names are equal, the employee with a higher salary should be printed out first. It sorts the List alphabetically, but doesn't check if the salary is bigger. What do I need to change?
ArrayList<Employee> employees = new ArrayList<Employee>();
public void sortEmployees(){
Collections.sort(employees, (p1, p2) -> p1.name.compareTo(p2.name));
for(Employee employee: employees){
Comparator.comparing(object -> employee.name).thenComparingDouble(object -> employee.grossSalary);
System.out.println("ID: " + employee.ID + END_OF_LINE + "Name: "+employee.name + END_OF_LINE + "Salary: " + employee.grossSalary);
System.out.println(""); // just an empty line
}
}

Change the method to be valid java code
public void promoteEmployee(UUID uniqueID){
but as it even seems to be a field, why pass the value at all?
As for sorting see
Implementing Java Comparator

one passes variables from one class to another's methods by using the classname.method(arg) syntax.
public class JavaTeachMe2018
{
//variable in other class to be passed as a method argument
public static int startID = 0;
public static void main(String[] args)
{
// we are passing startID to anouther class's method
String[] currentEmployees = Corporation.createEmployee(startID);
System.out.println("Welcome " + currentEmployees[1] + " to the company as employee number " + currentEmployees[0]);
}
}// end class teachme
here is the second class
import java.util.Scanner;
public class Corporation
{
public static int createId(int startID)
{
// create unique id
int uniqueID = startID + 1;
return uniqueID;
}
public static String[] createEmployee(int startID)
{
// assign a variable to the return of the createId call
int employeeNumber = createId(startID);
System.out.println("Your assigned employee number is " + employeeNumber);
// get employee name
Scanner stdin = new Scanner(System.in);
System.out.print(" Enter Your Name : ");
String employeeName = stdin.nextLine();
String employees[] = {Integer.toString(employeeNumber), employeeName};
return employees;
}
}

How do i use the return statement of one method in another private method?

This is my Code that I have so far:
import java.util.*;
public class VoteRecorder
{
// Variables and instance variables
public static String nameCandidatePresident1;
public static String nameCandidatePresident2;
public static String nameCandidateVicePresident1;
public static String nameCandidateVicePresident2;
public static int votesCandidatePresident1;
public static int votesCandidatePresident2;
public static int votesCandidateVicePresident1;
public static int votesCandidateVicePresident2;
private int myVoteForPresident;
private int myVoteForVicePresident;
public VoteRecorder()
{
nameCandidatePresident1 = "null";
nameCandidatePresident2 = "null";
nameCandidateVicePresident1 = "null";
nameCandidateVicePresident2 = "null";
votesCandidatePresident1 = 0;
votesCandidatePresident2 = 0;
votesCandidateVicePresident1 = 0;
votesCandidateVicePresident2 = 0;
myVoteForPresident = 0;
myVoteForVicePresident = 0;
}
public void setCandidatesPresident(String name1, String name2)
{
nameCandidatePresident1 = name1;
nameCandidatePresident2 = name2;
}
public void setCandidatesVicePresident(String name1, String name2)
{
nameCandidateVicePresident1 = name1;
nameCandidateVicePresident2 = name2;
}
public static void resetVotes()
{
votesCandidatePresident1 = 0;
votesCandidatePresident2 = 0;
votesCandidateVicePresident1 = 0;
votesCandidateVicePresident2 = 0;
}
public static String getCurrentVotePresident()
{
return nameCandidatePresident1 + ":" + votesCandidatePresident1 + "\n" +
nameCandidatePresident2 + ":" + votesCandidatePresident2;
}
public static String getCurrentVoteVicePresident()
{
return nameCandidateVicePresident1 + ":" + votesCandidateVicePresident1 + "\n" +
nameCandidateVicePresident2 + ":" + votesCandidateVicePresident2;
}
public void getAndConfirmVotes()
{
}
private String getVotes()
{
Scanner keyboard = new Scanner(System.in);
System.out.println("please vote for a President or vice president " + nameCandidatePresident1 + ", " + nameCandidatePresident2 + ", " + nameCandidateVicePresident1
+ " or " + nameCandidateVicePresident2);
String presidentVote = keyboard.nextLine();
if (presidentVote.equalsIgnoreCase(nameCandidatePresident1))
return nameCandidatePresident1;
if(presidentVote.equalsIgnoreCase(nameCandidatePresident2))
return nameCandidatePresident1;
System.out.println("please vote for a Vice president " + nameCandidateVicePresident1 + " or" + nameCandidateVicePresident2);
String vicePresidentVote = keyboard.nextLine();
if(vicePresidentVote.equalsIgnoreCase(nameCandidateVicePresident1))
return nameCandidateVicePresident1;
if(vicePresidentVote.equalsIgnoreCase(nameCandidateVicePresident2))
return nameCandidateVicePresident2;
else
return "not a valid vote";
}
private boolean confirmVotes()
{
System.out.println("Your vote for President is:");
System.out.println("your vote for Vice President is:");
System.out.println("Is this correct? Yes or No?");
Scanner keyboard = new Scanner(System.in);
String answer = keyboard.nextLine();
if (answer.equalsIgnoreCase("Yes"))
return true;
else
return false;
}
private void recordVote()
{
puscode: If confirmVotes returns true, take the nameCandidate, and ++ to votesCandidate of the same type
Copy this If statement four times, one for each of the candidates, 2 president and 2 vp.
Else or If confirmvotes returns false, put output saying that the votes were not confirmed.
}
}
Say i had all this code, lets look at the method getVotes() and confrimVotes(), in getVotes() the user picks a candidate and than that candidate is returned. How would i get that return statement to show up else where in other methods? like in confirmVote() i want to do this
System.out.println("Your vote for President is: (PresidentialCandidate return statement");
But how can i do that?

This is not a direct answer to your question, but I think your code could be made a lot simpler by harnessing some of the power of object-oriented programming.
You are storing multiple types of information about 4 candidates for different positions as separate variables, and it's making your class very unwieldy.
A (in my opinion) better approach would be to have e.g. a Candidate class to store information about a single candidate, and then your classes could look as follows:
class Candidate {
String Name;
int votes;
}
class VoteRecorder {
Candidate[] presidents;
Candidate[] vicePresidents;
Candidate myVoteForPresident; //Or even make these both ints.
Candidate myVoteForVicePresident;
}
The classes can be further refined, but this will be a start. Any time you see multiple pieces of information that describe the same entity being repeated multiple times, it's a good indication that you could simplify your life by adding a class to represent them together instead.
Edit (to answer question specifically):
If you want to do effectively the following:
System.out.println("Your vote for President is: (PresidentialCandidate return statement");
You can write something like this:
String voteResult = getVotes();
System.out.println("Your vote for President is: " + voteResult);
Or in one line:
System.out.println("Your vote for President is: " + getVotes());
Each time you run this code though, it will prompt the user for input. If you want to save the result until next time as well, you will have to save it to an attribute, e.g. by having a string in your class, and assigning the value to it first. Then just use that later instead of the local variable voteResult.