I want to use the object person in the Librarian_Interface class, but this call the method login() in a loop. I think there is something I don't understand with java instance and I tried to get person with a constructor or methode but in vain. Thanks !
public class Login_Interface {
Person person;
public Login_Interface() {
db.initConnection();
person = login(db, in);
if (person != null)
{
Librarian_Interface a = new Librarian_Interface();
a.run();
}
}
public void run() {
}
public static Person login(DbConnection db, Scanner sc) {
Persons.setDbConnection(db);
Persons persons = Persons.getInstance();
System.out.print("\nEnter your Phone Number : ");
String phone = sc.nextLine();
System.out.print("\nEnter your Password : ");
String password = sc.nextLine();
return persons.login(phone, password);
}
}
public class Librarian_Interface {
public Librarian_Interface() {
// What I want
// System.out.print(person); or person.getAge(); ...
All you have to do is pass the person object to the Librarian_Interface constructor. then you can call methods getAge on it, etc.
public class Librarian implements Runnable {
private final Person person;
public Librarian(Person person) {
this.person = person;
}
#Override
public void run() {
int age = person.age();
// ... whatever else
}
}
By the way, the convention in Java is to use upper camel case for class names, with no underscores. So it would be better to name the class LibrarianInterface. Also, it's probably not the best idea to call it LibrarianInterface if it is in fact a class and not an interface.
Since Librarian has a public run method, it's a good idea to have it implement Runnable so that users of the class see how it is meant to be used.
Related
I’m sure I wasn’t clear enough in the title, clarifying everything here. I have a passenger booking a flight, I want to make a list in which the flights booked by the passenger will be stored.
This is the part of the code where the passenger completes the reservation, how do I make a new list and add a booked flight in it
#Override
public void payingFirstClassWithoutPromoCode(ArrayList<Flight> flightsList) {
System.out.println("Confirm buying ticket: (yes or no)");
String confirmation = scanner.nextLine();
if (confirmation.equalsIgnoreCase("yes")) {
if (selectedPassenger.getBalance() >= selectedFlight.getPriceForFirstClass()) {
System.out.println("Successful reserved!");
selectedPassenger.setBalance(selectedPassenger.getBalance() - selectedFlight.getPriceForFirstClass());
System.out.println(selectedPassenger.getFirstName() + "'s new balance is: " + selectedPassenger.getBalance());
} else {
noFundsAvailable(flightsList);
}
} else if (confirmation.equalsIgnoreCase("no")) {
cancellation(flightsList);
} else {
System.out.println("Wrong input!");
}
}
I think you can add a Flight field in your Passenger class, then do
selectedPassenger.setFlight(selectedFlight)
Here's the passenger class
class Passenger{
//other fields
Flight flight;
public void setFlight(Flight f){
this.flight = f;
}
If a passenger can have multiple flight, then declare a List in your passenger class, then do
selectedPassenger.getFlights().add(selectedFlight);
class Passenger{
//other fields
List<Flight> flight;
public Passenger(){
//don't forget to initialize flight list
flight = new ArrayList();
}
public List<Flight> getFlights(){
return this.flight ;
}
instead of fetching the whole list and adding it manually, you can have a method in your passenger class like
public void addFlight(Flight f){
this.flight.add(f);
}
then you can do
selectedPassenger.addFlight(selectedFlight);
You could design your Passenger class like this:
public class Passenger {
private String name;
private List<Flight> flights;
//Getter and setter for name
public Passenger(String name) {
this.name = name;
this.flights = new ArrayList<>();
}
public void addFlight(Flight flight) {
flights.add(flight);
}
}
On a side note, it might be worth refactoring your code. I note that you named your method payingFirstClassWithoutPromoCode(ArrayList<Flight> flightsList). I imagine you will have many more options, which means you will have to write multiple methods with very similar code.
It can be a good idea to make one method that can handle many different scenarios.
For example, you can add the ticket type (first/business/economy class) as an parameter in your method: payingWithoutPromoCode(ArrayList<Flight> flightsList, String ticketType).
It means you have to rewrite your method a little bit. In my example, you probably need to rewrite the methods in your Flight class. Instead of selectedFlight.getPriceForFirstClass() you can do selectedFlight.getPrice(ticketType).
The pet store program should start with the user being able to choose to adopt a pet or give a pet the to the shop. If the user wants to adopt a pet, they should be able to see either all available pets, unless they say they know what type of pet they want, then show only available pets of that type.
The 4 methods that will need to be created for this program should:
add new pets
get a pet adopted
show pets by type
show pets available for adoption
Object Class: Pets.java
import java.util.*;
public class Pets {
public static void main(String[] args){
private double age; // age of the animal (e.g. for 6 months the age would be .5)
private String petName; // name of the animal
private String aType; // the type of the pet (e.g. "bird", "dog", "cat", "fish", etc)
private int collarID; // id number for the pets
private boolean isAdopted = false; // truth of if the pet has been adopted or not
private String newOwner;
private Date adoptionDate;
public double getAge() {
return age;
}
public void setAge(double age) {
this.age = age;
}
public String getPetName() {
return petName;
}
public void setPetName(String petName) {
this.petName = petName;
}
public String getaType() {
return aType;
}
public void setaType(String aType) {
this.aType = aType;
}
public int getCollarId() {
return collarID;
}
public void setCollarId(int collarId) {
this.collarID = collarId;
}
public boolean isAdoptated() {
return isAdopted;
}
public void setAdoptated(boolean isAdoptated) {
this.isAdopted = isAdoptated;
}
public Date getAdoptionDate() {
return adoptionDate;
}
public void setAdoptionDate(Date adoptionDate) {
this.adoptionDate = adoptionDate;
}
#Override
public String toString() {
return "Pets [age=" + age + ", petName=" + petName + ", aType=" + aType + ", collarId=" + collarID
+ ", isAdoptated=" + isAdopted + ", adoptionDate=" + adoptionDate + "]";
}
}
}
You should define the data fields and methods inside the class, but not inside the main()-method. The main()-method is the entry point of your java application and could be used to create an instance of your Pets class.
e.g.:
public static void main(String[] args) {
Pets pet = new Pets();
}
This code is not compiling for 2 main reasons:
You are specifying access modifiers on variables inside a method (in this case main), which is forbidden;
You are writing methods (e.g. getAge) inside another method (main) and trying to return a variable (e.g. age) that is out of that scope, in fact the variable age is not known inside the getAge method, because it's declared in the main method.
You should move the variable declaration to class level, and then have all methods separated using those variables. I'll give you a sketch, not the complete solution:
import java.util.*;
public class Pets {
/* Insert all variable declarations here */
private double age;
/* Constructor if you need it */
public Pets(/* parameters you think you need */) {
// Set attributes when you declare a new Pets()
}
/* Insert all methods you need here */
public double getAge() {
return this.age;
}
The positioning of the main method - for what I've understoon from your description - should be placed outside this class, in another class where the whole application will start to run. The Pet class should serve only for anything concerning pets (the four methods you will need to implement and all getters/setters for retrieving private class variables).
You’ve happened to put about everything — private fields and public methods — inside you main method. That doesn’t make sense. Everything that is in your main, move it outside, right under the line public class Pets {. That should fix your compiler error.
I want to try a simple implementation of phonebook with arraylist in java.
First I made a class contains what the info. needed and second I want have another class which have methods like getting info and printing them.
and because I want to use array list this is what I've done so far, but the 'print' method keep giving me the error in for loop, is there any one who can help me to optimize my code and why I have this error.
this is the first class :
public class PhoneBook {
long number;
String name;
.
.
.
.
getter() and setter();
}
The second class with methods:
public class PhoneBookMethods {
ArrayList<PhoneBook> phoneBooks = new ArrayList<PhoneBook>();
public void getInfo(PhoneBook phoneBooks)
{
.
.
.
}
public void print(PhoneBook phoneBooks)
{
for (PhoneBook p: phoneBooks) {// this is where I got the error
//foreach not applicable to type 'PhoneBook'
System.out.print(p.getName());
....
}
}
}
In your for-each loop, change
for (PhoneBook p: phoneBooks)
to
for (PhoneBook p: this.phoneBooks)
so that you would be accessing the phoneBooks arraylist, not the argument of the print method.
EDIT:
You can use the "this" keyword to make your code much more "explicit".
For the example, in your case you have an argument called phoneBooks that has the same name as your ArrayList (member variable). So to explicitly differentiate between the two of them, use this.phonebooks to access the member variable phoneBooks(the ArrayList), and use phoneBooks to refer to the argument.
If you want to use instance variable phoneBooks then no need to pass any param in the method print().
public void print()
{
for (PhoneBook p: phoneBooks) {// this is where I got the error
//foreach not applicable to type 'PhoneBook'
System.out.print(p.getName());
....
}
}
OR if you really want to pass param rename the param name
public void print(ArrayList<PhoneBook> phoneBookList)
{
for (PhoneBook p: phoneBookList) {// this is where I got the error
//foreach not applicable to type 'PhoneBook'
System.out.print(p.getName());
....
}
}
public void print(PhoneBook phoneBooks)
Your parameter phoneBooks masks the field (the array) also named phoneBooks. So compiler tries to treat parameter as list and failes.
Actually at first you have some design issues. The way you think what is a PhoneBook is invalid. You should consider a phonebook something holds several phones on it. Therefore, you may have a phone class like below:
public class Phone {
private String number;
private String name;
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
And a phonebook class responsible for holding those phone objects:
public class PhoneBook extends ArrayList<Phone> {
#Override
public String toString() {
StringBuilder stringBuilder = new StringBuilder();
for (Phone phone : this) {
stringBuilder.append("----------------------------\n");
stringBuilder.append("Name:" + phone.getName() + "\n");
stringBuilder.append("Number:" + phone.getNumber() + "\n");
}
return stringBuilder.toString();
}
}
It is a arraylist of Phone, nothing more. Thus, you can add or remove a phone directly via phone book. This is how to use it:
public class MAIN {
public static void main(String[] args) {
Phone myPhone = new Phone();
myPhone.setName("Eray");
myPhone.setNumber("0533XXXXXXX");
Phone girlfriendPhone = new Phone();
girlfriendPhone.setName("Canan");
girlfriendPhone.setNumber("0544XXXXXXX");
Phone yourPhone = new Phone();
yourPhone.setName("Bita Mirshafiee");
yourPhone.setNumber("0599XXXXXXX");
PhoneBook phoneBook = new PhoneBook();
phoneBook.add(myPhone);
phoneBook.add(girlfriendPhone);
phoneBook.add(yourPhone);
System.out.println(phoneBook);
}
}
Finally, this is the output:
----------------------------
Name:Eray
Number:0533XXXXXXX
----------------------------
Name:Canan
Number:0544XXXXXXX
----------------------------
Name:Bita Mirshafiee
Number:0599XXXXXXX
Ok so this is what I have
public class Register {
public String propertyID;
public String PPSNumber;
Register(String aPropertyID, String aPPSNumber) {
propertyID = aPropertyID;
PPSNumber = aPPSNumber;
}
public void setPPSNumber(String aPPSNumber) {
PPSNumber = aPPSNumber;
}
public String getPPSNumber() {
return PPSNumber;
}
public String getPropertyID() {
return propertyID;
}
}
Then I have this
public static ArrayList<Register> registers = new ArrayList<Register>();
public static void main(String[] args) {
String userInput1 = "", userInput2 = "", userInput3 = "";
userInput1 = JOptionPane.showInputDialog("Enter your PPSNumber");
userInput2 = JOptionPane.showInputDialog("Enter your propID");
registers.add("number", "id");
}
I don't understand why It wont let me add to the ArrayList. Is there some way of adding class types to ArrayLists?
Try this instead :
registers.add(new Register("number","id"));
EDIT 1:
To answer your question, you can create a separate "register" and the use the getters :
Register aRegister = new Register("number","id");
registers.add(aRegister);
System.out.println(aRegister.getPropertyID()+" "+ aRegister.getPPSNumber());
Your List is of type Register so you need to add object of Register class only.
Nothing wrong in create as many Register objects as required.
You can implement toString() method inside Register class then the below sysout will work given the register variable is initialized with Register object. Check this How to override toString() properly in Java? to know about toString implementation.
System.out.println(register)
I am a beginner programmer and this is my first question on this forum.
I am writing a simple text adventure game using BlueJ as a compiler, and I am on a Mac. The problem I ran into is that I would like to make my code more self automated, but I cannot call a class with a string. The reason I want call the class and not have it all in an if function is so that I may incorporate more methods.
Here is how it will run currently:
public class textadventure {
public method(String room){
if(room==street){street.enterRoom();}
}
}
public class street{
public enterRoom(){
//do stuff and call other methods
}
}
The if statement tests for every class/room I create. What I would like the code to do is automatically make the string room into a class name that can be called. So it may act like so:
Public method(string room){
Class Room = room;
Room.enterRoom();
}
I have already looked into using Class.forName, but all the examples were too general for me to understand how to use the function. Any help would be greatly appreciated, and if there is any other necessary information (such as more example code) I am happy to provide it.
-Sebastien
Here is the full code:
import java.awt.*;
import javax.swing.*;
public class Player extends JApplet{
public String textOnScreen;
public void start(){
room("street1");
}
public void room(String room){
if(room=="street1"){
textOnScreen=street1.enterRoom();
repaint();
}
if(room=="street2"){
textOnScreen=street2.enterRoom();
repaint();
}
}
public void paint(Graphics g){
g.drawString(textOnScreen,5,15);
}
}
public abstract class street1
{
private static String textToScreen;
public static String enterRoom(){
textToScreen = "You are on a street running from North to South.";
return textToScreen;
}
}
public abstract class street2
{
private static String textToScreen;
public static String enterRoom(){
textToScreen = "You are on another street.";
return textToScreen;
}
}
Seeing as you are rather new to programming, I would recommend starting with some programs that are simpler than a full-fledged adventure game. You still haven't fully grasped some of the fundamentals of the Java syntax. Take, for example, the HelloWorld program:
public class HelloWorld {
public static void main(String[] args) {
String output = "Hello World!"
System.out.println(output);
}
}
Notice that public is lowercased. Public with a capital P is not the same as public.
Also notice that the String class has a capital S.* Again, capitalization matters, so string is not the same as String.
In addition, note that I didn't have to use String string = new String("string"). You can use String string = "string". This syntax runs faster and is easier to read.
When testing for string equality, you need to use String.equals instead of ==. This is because a == b checks for object equality (i.e. a and b occupy the same spot in memory) and stringOne.equals(stringTwo) checks to see if stringOne has the same characters in the same order as stringTwo regardless of where they are in memory.
Now, as for your question, I would recommend using either an Enum or a Map to keep track of which object to use.
For example:
public class Tester {
public enum Location {
ROOM_A("Room A", "You are going into Room A"),
ROOM_B("Room B", "You are going into Room B"),
OUTSIDE("Outside", "You are going outside");
private final String name;
private final String actionText;
private Location(String name, String actionText) {
this.name = name;
this.actionText = actionText;
}
public String getActionText() {
return this.actionText;
}
public String getName() {
return this.name;
}
public static Location findByName(String name) {
name = name.toUpperCase().replaceAll("\\s+", "_");
try {
return Enum.valueOf(Location.class, name);
} catch (IllegalArgumentException e) {
return null;
}
}
}
private Location currentLocation;
public void changeLocation(String locationName) {
Location location = Location.findByName(locationName);
if (location == null) {
System.out.println("Unknown room: " + locationName);
} else if (currentLocation != null && currentLocation.equals(location)) {
System.out.println("Already in room " + location.getName());
} else {
System.out.println(location.getActionText());
currentLocation = location;
}
}
public static void main(String[] args) {
Tester tester = new Tester();
tester.changeLocation("room a");
tester.changeLocation("room b");
tester.changeLocation("room c");
tester.changeLocation("room b");
tester.changeLocation("outside");
}
}
*This is the standard way of formating Java code. Class names are PascalCased while variable names are camelCased.
String className=getClassName();//Get class name from user here
String fnName=getMethodName();//Get function name from user here
Class params[] = {};
Object paramsObj[] = {};
Class thisClass = Class.forName(className);// get the Class
Object inst = thisClass.newInstance();// get an instance
// get the method
Method fn = thisClass.getDeclaredMethod(fnName, params);
// call the method
fn.invoke(inst, paramsObj);
The comments below your question are true - your code is very rough.
Anyway, if you have a method like
public void doSomething(String str) {
if (str.equals("whatever")) {
// do something
}
}
Then call it like
doSomething("whatever");
In Java, many classes have attributes, and you can and will often have multiple instances from the same class.
How would you identify which is which by name?
For example
class Room {
List<Monster> monsters = new ArrayList <Monster> ();
public Room (int monstercount) {
for (int i = 0; i < monstercount; ++i)
monsters.add (new Monster ());
}
// ...
}
Monsters can have attributes, and if one of them is dead, you can identify it more easily if you don't handle everything in Strings.