Question

Why does my program generate [] when viewing all guests names?


-----------------------------------------------
import java.util.*;

public class Delete extends Info {
    String name;
    int Id;
    int del;

    public Delete() {
    }
    public void display() {
        Scanner key = new Scanner(System.in);
        System.out.println("Input Customer Name: ");
        name = key.nextLine();
        System.out.println("Enter ID Number: ");
        Id = key.nextInt();
        System.out.println("Would you like to Delete? Enter 1 for yes or 2 for no. ");
        del = key.nextInt();
        if (del == 1) {
            int flag = 0;     //learned that exceptions were the best way to do this. Learned from book
            try {
                for (Object nameString : getList()) {

                    if (name.equalsIgnoreCase(name))// from array in info class, have to figure out how to get array from info
                    // class into this one.
                    {
                        flag = 1;
                        getList().remove(name);// also from the array in the info class

                    }
                }

                if (flag == 0) {
                    System.out.println("Incorrect name.");

                }
            } catch (Exception e) {
                System.out.println("List is empty");
            }
        } else {
            System.out.println("You have chosen not to delete.");
        }

    }
}

-------------------------------------------------

public class View extends Info {

    public View() {
        String dash = ("--------------------------------");
    }

    public void display() {
        System.out.println("Customer Log\n" + dash);
        Info info = new Info();
        System.out.println(info.getList());


    }

}

-------------------------------

import java.util.Date;
import java.util.*;

public class Info {
    String name;
    String dateOfBirth;
    String password;
    int menu;
    String idnumber = "0000000000";
    String deletion;
    final int IDEN_LENGTH = 9;
    final String BREAK_CODE = "XXX";
    int total = 0;
    final int smallSuite = 25;
    final int mediumSuite = 50;
    final int largeSuite = 75;
    String dash = ("----------------------------------");
     ArrayList names = new ArrayList();


    public void display() {
        Scanner input = new Scanner(System.in);
        Date date = new Date();
        String dec;
        do {
            System.out.println("Please answer the following Questions to Check In: ");
            names.add("John");
            System.out.println("Enter your Full Name: ");

            name = input.nextLine();
            names.add(name);
            System.out.println("Date of Birth 8 digits in m/d/y format: ");
            dateOfBirth = input.nextLine();

            System.out.println("Enter your Identification Card Number: ");
            idnumber = input.nextLine();
            if (idnumber.length() != IDEN_LENGTH) {
                System.out.println("Invalid Length");
                display();
            } else {
                System.out.println("IdNumber is set.");
            }
            System.out.println("Enter your E-Signature: ");
            password = input.nextLine();
            if (password.equalsIgnoreCase(name)) {
                System.out.println("E signature accepted.");
                System.out.println(dash);
                String insert = dateOfBirth.substring(0, 2) + "/" + dateOfBirth.substring(2, 4) + "/"
                        + dateOfBirth.substring(4, 8);
                String idInsert = "(" + idnumber.substring(0, 3) + ")" + " " + idnumber.substring(3, 5) + "-"
                        + idnumber.substring(6, 9);
                // JOptionPane.showMessageDialog()
                System.out.println("Your information:");
                System.out.println("Name: " + name);
                System.out.println(" Date Of Birth: " + insert);
                System.out.println(" ID#: " + idInsert);
                System.out.println(" E Signature: " + password);
                System.out.println();
                System.out.println(dash);
                System.out.println(" Suite Package Options ");
                System.out.println(" #1 Small (1-2 people): $25 ");
                System.out.println(" #2 Medium (1-4 people): $50 ");
                System.out.println(" #3 Large: (1-8 people)($75 ");
                System.out.println(" Enter Option Number: ");
                int packageOption = input.nextInt();
                input.nextLine();
                if (packageOption != 0) {
                    if (packageOption == 1) {
                        total += smallSuite;
                        System.out.println("You have selected a small suite.");
                    }
                    if (packageOption == 2) {
                        total += mediumSuite;
                        System.out.println("You have selected a medium suite.");
                    }
                    if (packageOption == 3) {
                        total += largeSuite;
                        System.out.println("You have selected a large suite.");
                    }
                    System.out.println("Your current total is $" + total);
                } else if (packageOption != 1 | packageOption != 2 | packageOption != 3) {
                    System.out.println("Please choose a valid package number.");
                }
            } else {
                System.out.println("Signature does not match the name. Try again.");
                display();
            }
            System.out.println("Add another visitor? Y/N");
            dec = input.nextLine();
        }while(!dec.equalsIgnoreCase("N"));
    }

    public String returnArray() {
        return (name);
    }

    public ArrayList getList() {
         for(int x = 0; x < names.size(); ++x)
             System.out.println("position " + x + " Name: " + names.get(x));
        return names;
    }

}

------------------------------

import java.util.*;

public class Main {
    public static void main(String[] args) {
        String dash = ("----------------------------------");
        Scanner input = new Scanner(System.in);
        Date date = new Date();
        String option;
        System.out.println(date);
        do {
            System.out.println("Welcome to the Hotel\n" + dash);
            System.out.println("1. Add A Visitor\n2. View all Visitors\n3. Delete a Visitor");
            System.out.println("Choose option Number: ");
            int menu = input.nextInt();
            input.nextLine();
            if (menu == 1) {
                Info in = new Info();
                in.display();
            }
            if (menu == 2) {
                View v = new View();
                v.display();
            }
            if (menu == 3) {
                Delete del = new Delete();
                del.display();
            } else if (menu != 1 && menu != 2 && menu != 3) {
                System.out.println("Menu number does not exist.");
            }
            System.out.println("Do you want to continue!(Y/N)");
            option = input.nextLine();
        }while(!option.equalsIgnoreCase("N"));
    }
}

Answer 1

-------Main.java-------------

import java.util.*;

public class Main {
   static int count=1;//required to create the ArrayList instance only once in Info class
public static void main(String[] args) {
String dash = ("----------------------------------");
Scanner input = new Scanner(System.in);
Date date = new Date();
String option;
  
System.out.println(date);
do {
System.out.println("Welcome to the Hotel\n" + dash);
System.out.println("1. Add A Visitor\n2. View all Visitors\n3. Delete a Visitor");
System.out.println("Choose option Number: ");
int menu = input.nextInt();
input.nextLine();
if (menu == 1) {
Info in = new Info();
in.display();
count--;
}
if (menu == 2) {
View v = new View();
v.display();
}
if (menu == 3) {
Delete del = new Delete();
del.display();
} else if (menu != 1 && menu != 2 && menu != 3) {
System.out.println("Menu number does not exist.");
}
System.out.println("Do you want to continue!(Y/N)");
option = input.nextLine();
}while(!option.equalsIgnoreCase("N"));
}
}

-------Info.java------------

import java.util.*;

public class Info {
String name;
String dateOfBirth;
String password;
int menu;
String idnumber = "0000000000";
String deletion;
final int IDEN_LENGTH = 9;
final String BREAK_CODE = "XXX";
int total = 0;
final int smallSuite = 25;
final int mediumSuite = 50;
final int largeSuite = 75;
String dash = ("----------------------------------");
static ArrayList<String> names;//made static to reference in any other java class

public Info() {

//initialize ArrayList only once
   if(Main.count==1)
   names=new ArrayList<String>();
}
public void display() {
Scanner input = new Scanner(System.in);
Date date = new Date();
String dec;
do {
System.out.println("Please answer the following Questions to Check In: ");
names.add("John");
System.out.println("Enter your Full Name: ");

name = input.nextLine();
names.add(name);
System.out.println("Date of Birth 8 digits in m/d/y format: ");
dateOfBirth = input.nextLine();

System.out.println("Enter your Identification Card Number: ");
idnumber = input.nextLine();
if (idnumber.length() != IDEN_LENGTH) {
System.out.println("Invalid Length");
display();
} else {
System.out.println("IdNumber is set.");
}
System.out.println("Enter your E-Signature: ");
password = input.nextLine();
if (password.equalsIgnoreCase(name)) {
System.out.println("E signature accepted.");
System.out.println(dash);
String insert = dateOfBirth.substring(0, 2) + "/" + dateOfBirth.substring(2, 4) + "/"
+ dateOfBirth.substring(4, 8);
String idInsert = "(" + idnumber.substring(0, 3) + ")" + " " + idnumber.substring(3, 5) + "-"
+ idnumber.substring(6, 9);
// JOptionPane.showMessageDialog()
System.out.println("Your information:");
System.out.println("Name: " + name);
System.out.println(" Date Of Birth: " + insert);
System.out.println(" ID#: " + idInsert);
System.out.println(" E Signature: " + password);
System.out.println();
System.out.println(dash);
System.out.println(" Suite Package Options ");
System.out.println(" #1 Small (1-2 people): $25 ");
System.out.println(" #2 Medium (1-4 people): $50 ");
System.out.println(" #3 Large: (1-8 people)($75 ");
System.out.println(" Enter Option Number: ");
int packageOption = input.nextInt();
input.nextLine();
if (packageOption != 0) {
if (packageOption == 1) {
total += smallSuite;
System.out.println("You have selected a small suite.");
}
if (packageOption == 2) {
total += mediumSuite;
System.out.println("You have selected a medium suite.");
}
if (packageOption == 3) {
total += largeSuite;
System.out.println("You have selected a large suite.");
}
System.out.println("Your current total is $" + total);
} else if (packageOption != 1 | packageOption != 2 | packageOption != 3) {
System.out.println("Please choose a valid package number.");
}
} else {
System.out.println("Signature does not match the name. Try again.");
display();
}
System.out.println("Add another visitor? Y/N");
dec = input.nextLine();
}while(!dec.equalsIgnoreCase("N"));
}

public String returnArray() {
return (name);
}

public static ArrayList getList() { //made static to directly reference in other classes
for(int x = 0; x < names.size(); ++x)
System.out.println("position " + x + " Name: " + names.get(x));
return names;
}

}

--------------------View.java----------------

public class View extends Info {

public View() {
String dash = ("--------------------------------");
}
@Override
public void display() {
System.out.println("Customer Log\n" + dash);
//Info info = new Info();
System.out.println(Info.getList());//directly calls the function with class name

}

}

Problem with the code is "Info info = new Info();" this particular statement. Since you was creating the new object of Info class even the ArrayList also used to be initialized to null, which means there is no data to print it. Even after making the suggested changes if you method with object reference it won't work, as it will assume it as different object itself.