I am trying to write a program which stores information about a person in a linked list. I made a simple person class to store the name, age and addresses in the list. I would also like to store multiple addresses for EACH person, and a fact about the place in another linked list, inside the person class.
So for example, "Tara" can have a home address of "10 Central Ave" and a work address of "5 Willow street" etc. The problem is, I don't know how to have a linked list inside another.
My goal is to check whether the person's name is already on the list, and if so, add another address for them. (So that there is no repeats). I am a beginner and can really use some help.
public class Person {
private String name;
private int age;
public LinkedList <String> adresses;
public Person() {
name = "default";
age = 0;
adresses = new LinkedList<>();
}
public Person(String n, int a) {
name = n;
age = a;
}
public LinkedList<Adress> getAdresses() {
return adresses;
}
public void setAdresses(LinkedList<Adress> adresses) {
this.adresses = adresses;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String toString() {
return name+" "+age+" "+adresses;
}
}
public class Adress {
public String adress;
public String fact;
public Adress(String a, String f) {
adress = a;
fact = f;
}
public String getAdress() {
return adress;
}
public void setAdress(String adress) {
this.adress = adress;
}
public String getFact() {
return fact;
}
public void setFact(String fact) {
this.fact = fact;
}
}
public class Test {
public static void main(String[] args) {
Person Tara = new Person("Tara",35);
Person Judah = new Person("Judah",28);
Person Mark = new Person("Mark",45);
Person Seth = new Person("Seth",23);
LinkedList<Object> tester = new LinkedList<>();
tester.add(Tara);
tester.add(Judah);
tester.addLast(Mark);
tester.addLast(Seth);
System.out.println(tester);
}
}
How is about to use the next classic data structure for your project?
public class Person {
private String name
private int age;
public List<Address> addresses;
//...
}
Related
"This question is for a free online course I am taking. Below is the instructors direction and below that is my answer. I must be solving the problem wrong because the automatic grading system marks it incorrect even though I got the correct output. I believe the instructor wanted me to fill an array in the Main class with objects from the person class and I am unsure how to do that. Please help if you know how to do that or if you have a better idea of what the instructor wanted."
Instructors direction
In your main method, make an array of type Person Fill it with Person objects of the following people and then print the names of each from that array. Each person should be on their own line formatted as shown below.
Fred, 24
Sally, 26
Billy, 15
main.java
class Main {
public static Person[] people;
public static void main(String[] args) {
Person personObject = new Person();
personObject.Person();
}
}
Person.java
public class Person{
public static String[] Person(){
String[] people = {"Fred, 24", "Sally, 26", "Billy, 15"};
for(int i=0; i< people.length; i++){
System.out.println(people[i]);
}
return people;
}
}
It says you need objects and array. So i guess you wanted something like this.
Person.java
public class Person {
private String name;
private int age;
public Person(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
#Override
public String toString() {
return "Person{" + "name=" + name + ", age=" + age + '}';
}
}
By declaring Person p1 = new Person("Sally",26); you are creating object of class Person. You can use that as many times as you want and create different objects. We use override method toString to print informations about Person. We could also use p1.getName() and p1.getAge()
Main
public static void main(String[] args) {
Person p1 = new Person("Fred", 24);
Person p2 = new Person("Sally", 26);
Person p3 = new Person("Billy", 55);
Person[] people = {p1,p2,p3};
for(Person p : people){
System.out.println(p.toString());
}
}
I think what your professor wants is something like this :)
public class Runner {
public static void main(String args[])throws Exception{
Persons person1 = new Persons();
Persons person2 = new Persons();
Persons person3 = new Persons();
person1.setName("Fred");
person1.setAge("24");
person2.setName("Sally");
person2.setAge("26");
person3.setName("Billy");
person3.setAge("15");
String[] list = {person1.toString(), person2.toString(), person3.toString()};
for (int i = 0; i < list.length; i++) {
System.out.println(list[i]);
}
}
}
public class Persons {
private String name;
private String age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
#Override
public String toString() {
return name + ", " + age;
}
}
I'm trying to understand how to use the Java 8 Streams API.
For example, I have these two classes:
public class User {
private String name;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
}
public class UserWithAge {
private String name;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
private int age;
public int getAge() { return age; }
public void setAge(int age) { this.age = age; }
}
I have a List<User> of ten users, and I want to convert this to a List<UserWithAge> of ten users with the same names and with a constant age (say, 27). How can I do that using the Java 8 Streams API (without loops, and without modifying the above classes)?
You could use the map() feature of the stream to convert each User instance in your list to a UserWithAge instance.
List<User> userList = ... // your list
List<UserWithAge> usersWithAgeList = userList.stream()
.map(user -> {
// create UserWithAge instance and copy user name
UserWithAge userWithAge = new UserWithAge();
userWithAge.setName(user.getName());
userWithAge.setAge(27);
return userWithAge;
})
.collect(Collectors.toList()); // return the UserWithAge's as a list
While you could do this, You should not do like this.
List<UserWithAge> userWithAgeList = new ArrayList<UserWithAge>();
userList.stream().forEach(user -> {
UserWithAge userWithAge = new UserWithAge();
userWithAge.setName(user.getName());
userWithAge.setAge(27);
userWithAgeList.add(userWithAge);
});
public class ListIteratorExp {
public static void main(String[] args) {
List<Person> list = new ArrayList<>();
Person p1 = new Person();
p1.setName("foo");
Person p2 = new Person();
p2.setName("bee");
list.add(p1);
list.add(p2);
list.stream().forEach(p -> {
String name = p.getName();
System.out.println(name);
});
}
}
class Person{
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
output:-
vishal
thakur
Is it possible to protect from performing code placed in superclass constructor? In this example the output is
From Person
From Student
but I don't need to print out From Person. If I delete super(a, n); then program will not compile. Is it possible to print out only message from subclass?
class Person {
private int age;
private String name;
public Person(int a, String n) {
this.age = a;
this.name = n;
System.out.println("From Person");
}
public int getAge() {
return age;
}
public void setAge(int a) {
this.age = a;
}
public String getName() {
return name;
}
public void setName(String n) {
this.name = n;
}
}
class Student extends Person {
private String specialization;
public Student(int a, String n, String s) {
super(a, n);
specialization = s;
System.out.println("From Student");
}
public String getSpecialization() {
return specialization;
}
public void setSpecialization(String s) {
this.specialization = s;
}
}
public class Classes {
public static void main(String[] args) {
Student student_Jack = new Student(20, "Jack", "IT");
}
}
Instead of using super(a,n) you should use your methods for setting those variables that you have made.
public Student(int a, String n, String s) {
setAge(a);
setName(n);
specialization = s;
System.out.println("From Student");
}
You must also add an empty constructor in person.
public Person(){}
This will give you the same functionality, without needing to call the super constructor.
I have two classes: profesor and subject
public class Profesor {
private int numbClassroom;
public Profesor(int numbClassroom) {
this.numbClassroom = numbClassroom;
}
public int getNumbClassroom() {
return numbClassroom;
}
public void setNumbClassroom(int numbClassroom) {
this.numbClassroom = numbClassroom;
}
public String ToString(){
return "Number of classroom: "+numbClassroom;
} }
The second class is:
public class Subject{
String name;
Profesor lecturer = new Profesor();
Date yearOfStudy;
public void Dodeli(Profesor p){
??????
}}
I do not know how to add professor like a lecturer to a current subject
Like this? I don't see any problem.
public void Dodeli(Profesor p){
lecturer = p;
}
Profesor lecturer = new Profesor();
No need to instantiate lecturer. Just declare it. Then have getter/setter methods for it
Then you can assign Professor to Subject
Subject subj = new Subject("OOP"); //assuming you have corresponding constructor
subj.setLecturer(new Professor()); //or if you have existing prof object
Maybe require something like this : try to encapsulate your code
public class Professor {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
public class Subject{
private String name;
private Professor professor;
private int numbClassroom;
private Date yearOfStudy;
public int getNumbClassroom() {
return numbClassroom;
}
public void setNumbClassroom(int numbClassroom) {
this.numbClassroom = numbClassroom;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Professor getProfesor() {
return professor;
}
public void setProfesor(Professor profesor) {
this.professor = profesor;
}
public void Dodeli(){
System.out.println("Pofessor "+getProfesor().getName()+" is teaching "+getName()+" in Room NO :"+getNumbClassroom());
}
}
public class TestImpl {
public static void main(String arr[])
{
Subject subject = new Subject();
Professor professor = new Professor();
subject.setName("Biology");
professor.setName("MR.X");
subject.setNumbClassroom(1111);
subject.setProfesor(professor);
subject.Dodeli();
}
}
I have a class named Person.This class represents (as the name says) a Person. Now I have to create a class PhoneBook to represent a list of Persons. How can I do this? I don't understand what means "create a class to represent a list".
import java.util.*;
public class Person {
private String surname;
private String name;
private String title;
private String mail_addr;
private String company;
private String position;
private int homephone;
private int officephone;
private int cellphone;
private Collection<OtherPhoneBook> otherphonebooklist;
public Person(String surname,String name,String title,String mail_addr,String company,String position){
this.surname=surname;
this.name=name;
this.title=title;
this.mail_addr=mail_addr;
this.company=company;
this.position=position;
otherphonebooklist=new ArrayList<OtherPhoneBook>();
}
public String getSurname(){
return surname;
}
public String getName(){
return name;
}
public String getTitle(){
return title;
}
public String getMailAddr(){
return company;
}
public String getCompany(){
return position;
}
public void setHomePhone(int hp){
homephone=hp;
}
public void setOfficePhone(int op){
officephone=op;
}
public void setCellPhone(int cp){
cellphone=cp;
}
public int getHomePhone(){
return homephone;
}
public int getOfficePhone(){
return officephone;
}
public int getCellPhone(){
return cellphone;
}
public Collection<OtherPhoneBook> getOtherPhoneBook(){
return otherphonebooklist;
}
public String toString(){
String temp="";
temp+="\nSurname: "+surname;
temp+="\nName: "+name;
temp+="\nTitle: "+title;
temp+="\nMail Address: "+mail_addr;
temp+="\nCompany: "+company;
temp+="\nPosition: "+position;
return temp;
}
}
Your PhoneBook class will likely have a member like this:
private List<Person> book = new ArrayList<Person>();
And methods for adding and retrieving Person objects to/from this list:
public void add(final Person person) {
this.book.add(person);
}
public Person get(final Person person) {
int ind = this.book.indexOf(person);
return (ind != -1) ? this.book.get(ind) : null;
}
Note that a List isn't the best possible representation for a phone book, because (in the worst case) you'll need to traverse the entire list to look up a number.
There are many improvements/enhancements you could make. This should get you started.
Based on the class being named PhoneBook, I assume that you ultimately want to create a mapping between a phone number, and a person. If this is what you need to do then your PhoneBook class should contain a Map instead of a List (but this may depend on other parameters of the project).
public class PhoneBook
{
private Map<String,Person> people = new HashMap<String,Person>();
public void addPerson(String phoneNumber, Person person)
{
people.put(phoneNumber,person);
}
public void getPerson(String phoneNumber)
{
return people.get(phoneNumber);
}
}
In the above, the phone number is represented as a String, which is probably not ideal since the same phone number could have different String representations (different spacing, or dashes, etc). Ideally the Map key would be a PhoneNumber class that takes this all into account in its hashCode and equals functions.
you can do it by creating a class PhoneBook
public class PhoneBook{
Private List<Person> personList = new ArrayList<Person>;
public void addPerson(Person person){
this.personList.add(person);
}
public List getPersonList(){
return this.personList;
}
public Person getPersonByIndex(int index){
return this.personList.get(index);
}
}