We Keep Coding

How to access an object parameter from a hashmap value

I am trying to access the accOpBalance parameter from the Account method stored in the HashMap. I want to be able to change this value based on transaction type and store it again. I also want to save the the 6 most recent transactions fot the account but not sure how to approach the problem. I hope this describes the problem well enough. Im still very new to this and would love feedback on my code aswell.
public class BankingSystem{
static int accNum;
static String accName;
static String accAdd;
static String accOpDate;
static double accOpBalance;
int option = 0;
static Scanner keyboard = new Scanner(System.in);
static HashMap<Integer, Account> accounts = new HashMap<Integer, Account>(Map.of(
accNum, new Account(accNum, accName, accAdd, accOpDate, accOpBalance)
));
public BankingSystem() {
}
public static void main(String[] args) {
BankingSystem bankingSystem = new BankingSystem();
int option;
do{
option = mainMenu(keyboard);
System.out.println();
if(option == 1){
bankingSystem.createAccount(keyboard);
} else if (option == 2) {
bankingSystem.showAccounts();
} else if (option == 4) {
bankingSystem.deleteAccount();
}
}while(option != 5);
}
public void createAccount(Scanner keyboard) {
do{
System.out.println("-----------------------------------------------");
System.out.print("Please enter 1 to continue or -1 to exit: ");
option = keyboard.nextInt();
switch (option) {
case 1 -> {
Account newAccount = new Account(accNum, accName, accAdd, accOpDate, accOpBalance);
System.out.println("-----------------------------------------------");
System.out.print("Please enter the new account number: ");
accNum = keyboard.nextInt();
newAccount.setAccNum(accNum);
System.out.print("Please enter the name of the account holder: ");
accName = keyboard.next();
newAccount.setAccName(accName);
System.out.print("Please enter the address of the account holder: ");
accAdd = keyboard.next();
newAccount.setAccAdd(accAdd);
System.out.print("Please enter the accounts open date: ");
accOpDate = keyboard.next();
newAccount.setAccOpDate(accOpDate);
System.out.print("Please enter the starting balance: ");
accOpBalance = keyboard.nextDouble();
newAccount.setAccOpBalance(accOpBalance);
accounts.put(accNum, new Account(accNum, accName, accAdd, accOpDate, accOpBalance));
}
case 2 -> {
System.out.println("Please type -1 the exit create account menu: ");
option = keyboard.nextInt();
}
}
}while (option != -1);
}
public void showAccounts() {
for (Map.Entry<Integer, Account> accountEntry : accounts.entrySet()) {
System.out.println("Account key(number) = " + accountEntry.getKey() + accountEntry.getValue());
}
}
public void deleteAccount(){
int key;
option = 0;
do {
System.out.println("-----------------------------------------------");
System.out.print("Please enter 1 to continue or -1 to exit: ");
option = keyboard.nextInt();
switch (option) {
case 1 -> {
System.out.print("-----------------------------------------------");
System.out.print("Please enter the Account number of the" + "\n" +
" the account you wish to delete");
System.out.print("-----------------------------------------------");
key = keyboard.nextInt();
accounts.remove(key);
}
case 2 -> {
System.out.println("Please type -1 the exit delete account menu: ");
option = keyboard.nextInt();
}
}
}while (option != -1);
}
public static int mainMenu(Scanner keyboard){
int menuOption;
System.out.println("Welcome to the bank of Cal");
System.out.println("-----------------------------------------------");
System.out.println("Main Menu" + "\n" + "Please select option:");
System.out.println("1. Create Account");
System.out.println("2. Display Accounts");
System.out.println("3. Deposit/Withdraw");
System.out.println("4. Delete Account");
System.out.println("5. Exit Program");
System.out.println("-----------------------------------------------");
do{
menuOption = keyboard.nextInt();
}while(menuOption <1 || menuOption >5);
return menuOption;
}
public class Account {
private int accNum;
private String accName;
private String accAdd;
private String accOpDate;
private double accOpBalance;
Scanner getDetails = new Scanner(System.in);
public Account(int theAccNum, String theAccName, String theAccAdd, String theAccOpDate, double theAccOpBalance){
accNum = theAccNum;
accName = theAccName;
accAdd = theAccAdd;
accOpDate = theAccOpDate;
accOpBalance = theAccOpBalance;
}
public void setAccNum(int accNum){
this.accNum = accNum;
}
public int getAccNum(){
return accNum;
}
public void setAccName(String accName){
this.accName = accName;
}
public String getAccName(){
return accName;
}
public void setAccAdd(String accAdd){
this.accAdd = accAdd;
}
public String getAccAdd(){
return accAdd;
}
public void setAccOpDate(String accOpDate){
this.accOpDate = accOpDate;
}
public String getAccOpDate(){
return accOpDate;
}
public void setAccOpBalance(double accOpBalance){
this.accOpBalance = accOpBalance;
}
public double getAccOpBalance(){
return accOpBalance;
}
#Override
public String toString() {
return "\n" + "Account Number: " + accNum + "\n" + "Name: " + accName +
"\n" + "Account Holder Address: " + accAdd + "\n" +"Account open date: "
+ accOpDate + "\n" + "Account balance: " + accOpBalance;
}
}

May someone help me check how to create a list?

guys, am doing java programing and try to make a list, but i cannnot let it work as i expected, please help me find out where is wrong.
i have create the code on BlueJ and try to make main and method in different part, but when i try to add a variable in list, it seems added but wont present correctly, and remove method will call error and shut down the whole program
one is :
import java.util.ArrayList;
public class Plane
{
//Create 3 types of variables.
private String name;
private int safelength;
private short station;
private String passengername;
private static int seat;
private static int age;
private ArrayList<Passenger> Passengers;
public Plane(String psgname, int psgseat, int psgage)
{
psgname = passengername;
psgseat = seat;
psgage = age;
Passengers = new ArrayList<Passenger>();
}
public Plane(String planename, int maxlength, short astation)
{
name = planename;
safelength = maxlength;
station = astation;
}
public void addPassenger(Passenger Passenger)
{
Passengers.add(Passenger);
}
public void addPassenger(String passengernames, int pseat, int page)
{
Passengers.add(new Passenger(passengername, seat, page));
}
public Passenger findPassenger(String find)
{
for(Passenger ps : Passengers)
{
if(ps.getpname().contains(find))
{
return ps;
}
}
return null;
}
public int numberofPassenger()
{
return Passengers.size();
}
public void removePassenger(int number)
{
if (number >= 0 && number <numberofPassenger())
{
Passengers.remove(number);
}
}
public void listPassenger()
{
for(int index = 0; index < Passengers.size(); index++)
{
System.out.println(Passengers.get(index));
}
}
public void setname(String n)
{
name = n;
}
public String getname()
{
return name;
}
public void setsafelength(int s)
{
safelength = s;
}
public int getsafelength()
{
return safelength;
}
public void setstation(short a)
{
station = a;
}
public short getstation()
{
return station;
}
public String toString()
{
String text = "System checked, " + getname() + ", you can prepare yourself at station " + getstation() + " with the maxlength of " + getsafelength() + " metres.";
return text;
}
}
another one is :
import java.util.ArrayList;
import java.util.Scanner;
public class Passenger
{
// private varibales of the list.
private static String pname;
private static int seat;
private static int age;
public Passenger(String passengername, int pseat, int page)
{
// initialise instance variables
pname = passengername;
seat = pseat;
age = page;
}
public static void main(String[] args)
{
Plane p = new Plane("Joey", 45, 26);
String text = "Please select your option:\n" + "1.Add a passenger.\n" + "2.Find a passenger.\n" + "3.Total number of passengers.\n" + "4.Remove a passenger.\n" + "5.Print all passengers\n";;
System.out.println(text);
Scanner input = new Scanner(System.in);
int choice = input.nextInt();//waiting type the choice
if(choice > 5 || choice < 0)
{//if choice is wrong
System.out.println("Please select a vailable option!");
}
while(choice <=5 && choice >= 0)
{
if(choice == 1)
{
Scanner inputname = new Scanner(System.in);
System.out.println("Please enter the name of passenger");
String x = inputname.nextLine();
Scanner inputseat = new Scanner(System.in);
System.out.println("Please enter the number of seat.");
int y = inputseat.nextInt();
Scanner inputage = new Scanner(System.in);
System.out.println("Please enter the age of passenger.");
int z = inputage.nextInt();
Passenger padd = new Passenger(pname, seat, age);
p.addPassenger(padd);
System.out.println(text);
choice = input.nextInt();
}
if (choice == 2)
{System.out.println("Please enter the name you want to find.");
String a = input.nextLine();
p.findPassenger(a);
System.out.println(text);
choice = input.nextInt();
}
if (choice == 3)
{
p.numberofPassenger();
System.out.println(text);
choice = input.nextInt();
}
if (choice == 4)
{System.out.println("Please enter the number of list which one you want to remove.");
int b = input.nextInt();
p.removePassenger(b);
System.out.println(text);
choice = input.nextInt();
}
if (choice == 5)
{System.out.println("Here are all the variables of the list.");
p.listPassenger();
System.out.println(text);
choice = input.nextInt();
}
}
}
public static void setpname(String pn)
{
pname = pn;
}
public static String getpname()
{
return pname;
}
}

Problem 1.
public void listPassenger()
{
for(int index = 0; index < Passengers.size(); index++)
{
System.out.println(Passengers.get(index));
}
}
Here you are printing the value of instance variable,not the passenger's name.To print it, do
System.out.println(Passengers.get(index).getpname());
but this will return null,because your pname is static and you have never initialized its value.For this,change all yor static varibales to non-static.
Problem 2.
Passenger padd = new Passenger(pname, seat, age);
you are storing passenger's name seat age in x y zvariables respectively,butduring the creation of Passenger ,you are using pname seat age variables, which are null.So here do
Passenger padd = new Passenger(x, y, z);
At last,change every static variable and methods to non-static.
Final Solution will look like this,
import java.util.ArrayList;
import java.util.Scanner;
public class Passenger
{
// private varibales of the list.
private String pname;
private int seat;
private int age;
public Passenger(String passengername, int pseat, int page)
{
// initialise instance variables
pname = passengername;
seat = pseat;
age = page;
}
public static void main(String[] args)
{
Plane p = new Plane("Joey", 45, 26);
String text = "Please select your option:\n" + "1.Add a passenger.\n" + "2.Find a passenger.\n" + "3.Total number of passengers.\n" + "4.Remove a passenger.\n" + "5.Print all passengers\n";;
System.out.println(text);
Scanner input = new Scanner(System.in);
int choice = input.nextInt();//waiting type the choice
if(choice > 5 || choice < 0)
{//if choice is wrong
System.out.println("Please select a vailable option!");
}
while(choice <=5 && choice >= 0)
{
if(choice == 1)
{
Scanner inputname = new Scanner(System.in);
System.out.println("Please enter the name of passenger");
String x = inputname.nextLine();
Scanner inputseat = new Scanner(System.in);
System.out.println("Please enter the number of seat.");
int y = inputseat.nextInt();
Scanner inputage = new Scanner(System.in);
System.out.println("Please enter the age of passenger.");
int z = inputage.nextInt();
Passenger padd = new Passenger(x, y, z);
p.addPassenger(padd);
System.out.println(text);
choice = input.nextInt();
}
if (choice == 2)
{System.out.println("Please enter the name you want to find.");
String a = input.nextLine();
p.findPassenger(a);
System.out.println(text);
choice = input.nextInt();
}
if (choice == 3)
{
p.numberofPassenger();
System.out.println(text);
choice = input.nextInt();
}
if (choice == 4)
{System.out.println("Please enter the number of list which one you want to remove.");
int b = input.nextInt();
p.removePassenger(b);
System.out.println(text);
choice = input.nextInt();
}
if (choice == 5)
{System.out.println("Here are all the variables of the list.");
p.listPassenger();
System.out.println(text);
choice = input.nextInt();
}
}
}
public void setpname(String pn)
{
pname = pn;
}
public String getpname()
{
return pname;
}
}

Why is my program not accepting input through the console? (Java)

I know it's a silly silly program. It's just to practice constructors.
public class PetRecord {
private String name = "Bob";
private int age;
private double weight;
public PetRecord(String initialName, int initialAge, double initialWeight) {
name = initialName;
if(initialAge < 0 || weight < 0) {
System.out.println("Error: Age or weight cannot be negative");
System.exit(0);
}
else {
age = initialAge;
weight = initialWeight;
}
}
public PetRecord(String initialName) {
name = initialName;
}
public void output() {
System.out.println("Name: " + name);
System.out.println("Age: " + age);
System.out.println("Weight: " + weight);
}
public void setAll(String newName, int newAge, double newWeight) {
name = newName;
if ((newAge < 0) || (newWeight < 0)) {
System.out.println("Error: Negative age or weight.");
System.exit(0);
}
else {
age = newAge;
weight = newWeight;
}
}
public void review() {
if(age < 8 && weight < 8) {
System.out.println("Your pets weight and age are healthy.");
}
if(age >= 8 && weight >=8) {
System.out.println("Your pets weight and age are unhealthy.");
}
else {
System.out.println("Come to my office for a proper assessment.");
}
}
}
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
PetRecord d = new PetRecord("Bob");
System.out.println("Please check if our current records are correct.");
d.output();
System.out.println("Are they correct?");
String answer = input.nextLine();
String yes = "Yes";
String no = "No";
if((answer.equals(yes))) {
System.exit(0);
}
if(answer.equals(no)) {
System.out.println("Please enter your pets name.");
String correctName = input.nextLine();
System.out.println("Age?");
int correctAge = input.nextInt();
System.out.println("Weight?");
double correctWeight = input.nextDouble();
d.setAll(correctName, correctAge, correctWeight);
System.out.println("Your updated records say: ");
d.output();
System.out.println("Would you like a health review?");
String answer1 = input.nextLine();
String yes1 = "yes";
String no1 = "no";
if(answer1.equals(yes1)) {
d.review();
}
if(answer1.equals(no1)) {
System.out.println("Thank you for using PetSystem. Goodbye.");
System.exit(0);
}
}
}
}
My program accepts input for String answer, but my program will not accept String answer1. I can't even type anything in the console after the program asks you if you would like a health review.

The issue comes from here
System.out.println("Your updated records say: ");
d.output();
Because you have printed something out in the middle of accepting input, you most likely have an extra newline token you have not dealt with. Prior to asking the "health review" question place the following code.
while (input.hasNextLine()) {
input.nextLine();
}
This will make sure that you clear out any extra tokens before continuing to accept user input.

you can,t type anything in the console after "if you would like a health review." because you code only runs ones you should put it in a loop to make it run more than once

driver class what to do (array)

I am trying to create a driver class using array list of objects and it requires me to :
Read the book title from the user
Read the book ISBN from the user
Read the book in stock quantity from the user
program should continue to read the book information from the user until all the entries from the user for all the fields are blank or zero.
program will store valid book objects into an ArrayList (only valid objects)
Your program will then print the list all the "valid" Books entered by the user in the reverse order in which the books were entered.
As the user is entering information, the program should give feedback such as reporting that an item has been added to the ArrayList, or reporting any errors found.
Books with invalid entries were not added to the ArrayList, therefore they will not be printed when the ArrayList is printed
Here is my current code so far for my driver: (I'm a bit newb at this so )
edited: with the answer given
Here is what I got now
import java.io.*;
import java.util.*;
public class Bookstore2{
public static void main(String arg[ ]) throws Exception{
Scanner sc = new Scanner(System.in);
int isbn=0;
int quantity = 0;
String title = "";
Book oneBook;
List<Book> bookList = new ArrayList<Book>(); //here
while(true){
System.out.print("Enter title: ");
title = sc.nextLine( );
sc = new Scanner(System.in);
System.out.println();
System.out.print("Enter isbn: ");
isbn = sc.nextInt( );
sc = new Scanner(System.in);
System.out.println();
System.out.print("Enter quantity: ");
quantity = sc.nextInt( );
sc = new Scanner(System.in);
sc = new Scanner(System.in);
System.out.println();
// WRITE YOUR VALIDATION CODE HERE
// Change condition according to your requirements.
if(isbn !=0 && quantity != 0 && title != null && title != "")
{
oneBook = new Book(title, isbn, quantity);
bookList.add(oneBook); //create a list in main
System.out.println("Book added in the list.");
}
else
{
System.out.println("Book not added");
break;
}
}
for(int i = bookList.size()-1; i >= 0; i--){
System.out.println(bookList.get(i));
}
} //main method
} //class
error now averted but it's not utilizing both my exception and book class it seems like
Here is my class and my exception that will be running with the new driver class
-----Class
public class Book{
//instance variables
private String title = "";
private int isbn;
private int quantity;
public Book (String title, int isbn, int quantity)throws BookException{
//constructors
setTitle(title);
setIsbn(isbn);
setQuantity(quantity);
}
public String toString( ){ //toString Method
String s = "";
s = s + "Title: " + this.title + "\nISBN: " + this.isbn + "\nQuantity: " + this.quantity + "\n";
return s;
}
public String getTitle( ){
return this.title;
}
public int getisbn( ){
return this.isbn;
}
public int getquantity( ){
return this.quantity;
}
//mutator methods
public void setTitle(String newtitle )throws BookException{
if(newtitle.length()<1){
BookException be = new BookException( );
be.setMessage("Title cannot be blank");
throw be;
}
else{
this.title=newtitle;
}
}
public void setIsbn(int newisbn)throws BookException{
if (isbn <= 1000 || isbn >= 10000) {
this.isbn = newisbn;
}
else{
BookException be = new BookException( );
be.setMessage("ISBN should be between 1000 and 10000.");
throw be;
}
}
public void setQuantity(int newquantity)throws BookException{
if(newquantity>=0){
this.quantity = newquantity;
}
else{
BookException be = new BookException( );
be.setMessage("Quantity can't be a negative number.");
throw be;
}
}
}
------Exception Class
public class BookException extends Exception {
//instance variable
private String message = "";
public void setMessage(String newMessage) {
this.message = newMessage;
}
public String getMessage() {
return this.message;
}
}

First of all use: while(true) loop to iterate until user entered 0 for all the field.
while(true)
{
// Scanner Code i.e. read input from the user.
if(//check all the inputs)
{
//create a new book and insert it into array list
}
else
{
// If input is 0, break from the loop
}
}
Secondly, Never perform validation in your bean class. Create a separate class or method to validate the inputs. After, input validation only then create a new object.
Hope this will help you.
The correct code :
sc = new Scanner(System.in);
while(true){
System.out.print("Enter title: ");
title = sc.nextLine( );
System.out.println();
System.out.print("Enter isbn: ");
isbn = sc.nextInt( );
System.out.println();
System.out.print("Enter quantity: ");
quantity = sc.nextInt( );
System.out.println();
// WRITE YOUR VALIDATION CODE HERE
// Change condition according to your requirements.
if(isbn !=0 && quantity != 0 && title != null && title != "")
{
oneBook = new Book(title, isbn, quantity);
bookList.add(oneBook); //create a list in main
System.out.println("Book added in the list.");
}
else
{
System.out.println("Book not added");
break;
}
}
for(int i = bookList.size()-1; i >= 0; i--){
System.out.println(bookList.get(i));
}

You posted :
while(title != null || title.equals("0") || isbn != null || isbn != 0 || quantity
isbn is of int type i.e. primitive type how can we compare it with a null.
quantity is also of int type.
Default value of an int i.e. primitive type is 0. And, primitive type can never be compared with null.

Since there is so much confusion on the code, here is a complete solution to the task:
Bookstore.java:
public class Bookstore {
static final Scanner in = new Scanner(System.in);
static List<Book> books = new ArrayList<>();
public static void main(String arg[]) throws Exception {
while (true) {
// read book information
Book book = new Book();
System.out.print("Enter title: ");
book.title = in.nextLine();
System.out.println();
System.out.print("Enter ISBN: ");
book.isbn = readInt();
System.out.println();
System.out.print("Enter quantity: ");
book.quantity = readInt();
System.out.println();
// exit condition: "blank book" entered
if (book.title.isEmpty() && book.isbn == 0 && book.quantity == 0) {
System.out.println("Goodbye!");
break;
}
//validate and add book
try {
validateBook(book);
books.add(book);
System.out.println("Book successfully added to the list.");
} catch (IllegalStateException ex) {
System.err.println("Book is not valid: " + ex.getMessage());
continue;
}
// print book list
for (int i = books.size() - 1; i >= 0; i--) {
System.out.println(books.get(i));
System.out.println();
}
}
}
static int readInt() {
while (true) {
String input = in.nextLine();
if(input.isEmpty()) {
return 0;
}
try {
return Integer.parseInt(input);
} catch (NumberFormatException ex) {
System.err.println("Expected a valid integer: " + input);
}
}
}
static void validateBook(Book book) {
if (book.title == null || book.title.isEmpty()) {
throw new IllegalStateException("Book title must not be blank.");
}
if (book.isbn < 1000 || book.isbn > 10000) {
throw new IllegalStateException("Book ISBN must be between 1000 and 10000.");
}
if (book.quantity < 0) {
throw new IllegalStateException("Book quantity must be positive.");
}
}
}
Book.java:
public class Book {
public String title;
public int isbn;
public int quantity;
#Override
public String toString() {
return String.join("\n",
"Title: " + title,
"ISBN: " + isbn,
"Quantity: " + quantity
);
}
}

Why is my program repeating itself. Java Error

I am supposed to make the program give the number of pets and the percentage of how many that are below 5lbs, 5-10lbs, and over 10lbs. The program keeps repeating the statements and I don't know why. I've been working on this problem for the past couple of days and I still can't figure it out. At times it seems like I fixed it but then later on it happens again. Can anyone clarify why this is happening? I need help please.
import java.util.*;
import java.util.Collections;
import java.util.Comparator;
import java.lang.Object;
public class SetPetWeight
{
public static void main(String[] args) {
ArrayList<Pet> list = new ArrayList<Pet>();
String name;
String answer;
int age;
Double weight;
Scanner keyboard = new Scanner(System.in);
do
{
System.out.println("Enter a String for Pet name: ");
name = keyboard.next();
System.out.println("Enter an int for Pet age: ");
age = keyboard.nextInt();
if(age <= 0)
System.out.println("Error! Enter a real age");
System.out.println("Enter a double for Pet weight: ");
weight = keyboard.nextDouble();
if(weight <= 0)
System.out.println("Error! Enter a real weight");
do
{
System.out.println("Do you want to enter another pet? Y/N");
answer = keyboard.nextLine();
keyboard.nextLine();
} while (answer.equalsIgnoreCase("Y"));
} while (name.length() < 0 && age < 0 && weight < 0);
System.out.println("The weight is now sorted by weight!");
Collections.sort(list, Pet.SortByWeight);
for (Pet p2 : list)
p2.writeOutput();
int average1 = 0;
int average2 = 0;
int average3 = 0;
for (Pet p : list)
{
if(p.getWeight() >= 0 && p.getWeight() <= 5)
{
++average1;
}
else if(p.getWeight() >= 5 && p.getWeight() <= 10)
{
++average2;
}
else if(p.getWeight() > 10)
{
++average3;
}
System.out.println("The average of pets under 5 pounds:" + average1);
System.out.println("The average of pets between 5 and 10 pounds:" + average2);
System.out.println("The average of pets over 10 pounds:" + average3);
}
}
}
Pet Class that is used for the SetPetWeight class and is compiled correctly and is used for the array.
import java.util.*;
public class Pet {
private String name;
private Integer age; // in years
private double weight; // in pounds
public void writeOutput() {
System.out.println("Name: " + name);
System.out.println("Age: " + age + " years");
System.out.println("Weight: " + weight + " pounds");
}
public void set(String newName) {
name = newName;
// age and weight are unchanged.
}
public void set(int newAge) {
if (newAge <= 0) {
System.out.println("Error: illegal age.");
System.exit(0);
} else
age = newAge;
// name and weight are unchanged.
}
public void set(double newWeight) {
if (newWeight <= 0) {
System.out.println("Error: illegal weight.");
System.exit(0);
} else
weight = newWeight;
// name and age are unchanged.
}
public Pet(String name, int age, double weight) {
this.name = name;
this.age = age;
this.weight = weight;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
public double getWeight() {
return weight;
}
public static Comparator<Pet> SortByWeight = new Comparator<Pet>()
{
public int compare(Pet pet1, Pet pet2)
{
return (int)(pet1.getWeight() - pet2.getWeight());
}
};
}

Move keyboard.nextLine(); after weight = keyboard.nextDouble(); to consume the dangling newline character .

There are a few changes you may want to make.
1. Every time you retrieve user input for pet's name, age and weight. You may want to create an object of type pet to store this values and then add this to your ArrayList. Before you ask them if they wan to add another pet.
2. Remove the outer do while loop, and change the inter loop to include the "Enter a String for pet name: ".
3. Also check for validation for input.
do {
System.out.println("Enter a String for Pet name: ");
name = keyboard.next();
System.out.println("Enter an int for Pet age: ");
age = keyboard.nextInt();
if(age <= 0)
System.out.println("Error! Enter a real age");
System.out.println("Enter a double for Pet weight: ");
weight = keyboard.nextDouble();
keyboard.nextLine();
if(weight <= 0)
System.out.println("Error! Enter a real weight");
System.out.println("Do you want to enter another pet? Y/N");
answer = keyboard.nextLine();
keyboard.nextLine();
} while (answer.equalsIgnoreCase("Y"));