We Keep Coding

Write a Dog constructor that has one argument, the name, and calls the super constructor passing it the name and the animal type “dog”. cant pass type

public class Pet
{
private String name;
private String type;
public Pet(String n, String t)
{
name = n;
type = t;
}
public String getType(){
return type;
}
public String getName(){
return name;
}
public void speak()
{
System.out.println("grr!");
}
public static void main(String[] args)
{
Pet p = new Pet("Sammy","hamster");
System.out.println(p.getType());
p.speak();
Dog d = new Dog("Fido");
System.out.println(d.getType());
d.speak();
//Cat c = new Cat("Fluffy");
//System.out.println(c.getType());
//c.speak();
}
}
class Dog extends Pet
{
public Dog(String name){
super(name);
}
public void speak(){
System.out.println("Woof");
}
}
// Add a Cat class
How do I add "type" to this without adding another String to my parameter?
I've tried other ways that obviously didn't work but I still tried anyway. So how do I add another object to my super class from Pet without adding more to my parameter?

Constructor with one parameter for the dog class:
public Dog(String name) {
super(name, "dog");
}

Sending a List of different objects and returning the sum of their properties

I have to classes
public class Consumer{
private String name;
private int salary;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getSalary() {
return salary;
}
public void setSalary(int salary) {
this.salary = salary;
}
}
and next
public class Donor {
private String name;
private int amount;
private String location;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAmount() {
return amount;
}
public void setAmount(int amount) {
this.amount = amount;
}
}
now i have another class which contains a method method1()
public class GenericClass<T> {
public void method1(List<T> list){
Iterator i = list.iterator();
while (i.hasNext()){
}
}
}
and My main method is
public class MainMethod {
public static void main(String[] args) {
List<Donor> d = new ArrayList<>();
Donor donor = new Donor();
donor.setAmount(500);
donor.setName("bill");
Donor donor1 = new Donor();
donor.setAmount(1250);
donor.setName("linda");
d.add(donor);
d.add(donor1);
GenericClass genericClass = new GenericClass();
genericClass.method1(d);
}
}
i want to make this method1() dynamic and return a dynamic result.
so if i send the list of Consumer then it should return me the sum of all salaries and if i send the list of Donor then it should send me the sum of amount donated ?
how can this be achieved ?

First, you'd probably not make the class GenericClass generic but the method method1().
Then you could provide a ToIntFunction<T> which takes an object of type T and returns an int value. Thus your method could look like this (Java8 code):
public <T> int method1(List<T> list, ToIntFunction<T> transformation){
return list.stream().collect(Collectors.summingInt(transformation));
}
You'd then call that method like this:
int sumSalaries = method1(consumers, Consumer::getSalary);
int sumDonations = method1(donors, Donor::getAmount);
Pre-Java8 code would be possible as well but it would be a little bigger (you'd need to provide ToIntFunction, implementations of that interface and a slightly larger method body).
Alternatively you could use an Interface that's implemented by both classes but that would require you to use a common method name (e.g. getAmount() or getIntValue() etc.)

Why can't I accesses the properties of an object stored in a element of a ArrayList?

I have two packages lets give them the name package 1 and package 2.
Class A and Class B is in package1. Class A contains an ArrayList called PTable. Class B contains a function called query() that filters through PTable,in Class A, based on a certain conditions and returns an ArrayList called result that contains all the elements from PTable that meet that condition.
I now have package2 that contains Class C. Class C imports Class B from package 1; Class C is a subclass of HttpServlet. I create an object of Class B in class C and initializer it.
I then call the function query() and assign it to a variable called results. When I try and get the properties of an element at a certain index, I can't see the properties of the original objects stored in the ArrayList PTable.[This is what appears when I try and access the properties of the objects. My aim is to see the second image ][1]

Nice to ask questions but first spend sometime studying Java. Read a book or online and you will learn about casting very quickly. Also about classes, super classes etc
Your storing the objects in a variable of type Element (your results array list).
Cast the object back to the type it belongs too and then you will see the variables.
Code design note : storing different types of classesin the same array list is legal and possible but bug prone. Try to avoid it. If you change the order of storing variables into the list, you need to change all the access code too. Anyway happy learning.
There are free online Java tutorials study them -> https://www.google.co.in/search?q=java+tutorial+beginner
Sample class, in the main method try to get the object at position 1 and cast it to a Person :
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
class Person {
private String name;
private int age;
public Person() {
}
public Person(String name, int age) {
super();
this.age = age;
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
class Car {
private String manufacturer;
private String model;
private double price;
private int yearOfMfr;
private Date dateBought;
private String licenceNumber;
public Car() {
super();
}
public Car(String manufacturer, String model, double price, int yearOfMfr, Date dateBought, String licenceNumber) {
super();
this.manufacturer = manufacturer;
this.model = model;
this.price = price;
this.yearOfMfr = yearOfMfr;
this.dateBought = dateBought;
this.licenceNumber = licenceNumber;
}
public String getManufacturer() {
return manufacturer;
}
public void setManufacturer(String manufacturer) {
this.manufacturer = manufacturer;
}
public String getModel() {
return model;
}
public void setModel(String model) {
this.model = model;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public int getYearOfMfr() {
return yearOfMfr;
}
public void setYearOfMfr(int yearOfMfr) {
this.yearOfMfr = yearOfMfr;
}
public Date getDateBought() {
return dateBought;
}
public void setDateBought(Date dateBought) {
this.dateBought = dateBought;
}
public String getLicenceNumber() {
return licenceNumber;
}
public void setLicenceNumber(String licenceNumber) {
this.licenceNumber = licenceNumber;
}
}
public class DemoApp {
public static void main(String[] args) {
List<Object> results = new ArrayList<>();
DemoApp app = new DemoApp();
app.fillItUp(results);
Car acar = (Car) results.get(0);
acar.setLicenceNumber("Flying Duck");
}
private void fillItUp(List<Object> results) {
Car car = new Car("sel2in", "electric_VTOL", 540923, 2018, new Date(2018, 3, 32), "Skyprog");
results.add(car);
results.add(new Person("tushar", 39));
}
}

FlexJson serializing and deserializing an interface

I get an error trying to deserializing my data structure, which is a list of items, every one of them implements an interface. In addition, one of the fields of the interface is object, and every inheritance treats this Object as different field.
After so many hours spent on this issue, any answer will be appreciated.
This is the error I receive:
Exception in thread "main" java.lang.ClassCastException:
java.lang.String cannot be cast to java.util.Map
at flexjson.factories.BeanObjectFactory.instantiate(BeanObjectFactory.java:17)
at flexjson.ObjectBinder.bind(ObjectBinder.java:86)
at flexjson.ObjectBinder.bindIntoObject(ObjectBinder.java:139)
at flexjson.factories.ClassLocatorObjectFactory.instantiate(ClassLocatorObjectFactory.java:38)
at flexjson.ObjectBinder.bind(ObjectBinder.java:86)
at flexjson.ObjectBinder.bindIntoCollection(ObjectBinder.java:101)
at flexjson.factories.ListObjectFactory.instantiate(ListObjectFactory.java:13)
at flexjson.ObjectBinder.bind(ObjectBinder.java:86)
at flexjson.ObjectBinder.bind(ObjectBinder.java:65)
at flexjson.JSONDeserializer.deserialize(JSONDeserializer.java:158)
at testSerizlizeDeserializeInterface.entryPointForTestingSerialize.main(entryPointForTestingSerialize.java:34)
I made an example if anyone would like to try and play with it as well...
The interface
The EPersonType
The inheritance
The main class
The output
Thanks!
The interface
public interface IPerson {
EPersonType getPersonType();
String getName();
void setName(String name);
int getAge();
void setAge(int age);
Object getValue();
void setValue(Object value);
}
Its a pretty straightforward interface. The tricky part, as I already mentioned, is that the value represented as an Object, will contain different values based on interface implementation.
EPersonType
public enum EPersonType {
Father,
Mother,
}
The inheritance
public class Father implements IPerson {
private String name;
private int age;
private String value;
#Override
public String getName() {
return name;
}
#Override
public void setName(String name) {
this.name = name;
}
#Override
public int getAge() {
return age;
}
#Override
public void setAge(int age) {
this.age = age;
}
#Override
public Object getValue() {
return value;
}
#Override
public void setValue(Object value) {
this.value = (String) value;
}
#Override
public EPersonType getPersonType() {
return EPersonType.Father;
}
}
And another instance
public class Mother implements IPerson {
private String name;
private int age;
private boolean value;
#Override
public String getName() {
return name;
}
#Override
public void setName(String name) {
this.name = name;
}
#Override
public int getAge() {
return age;
}
#Override
public void setAge(int age) {
this.age = age;
}
#Override
public Object getValue() {
return value;
}
#Override
public void setValue(Object value) {
this.value = (boolean) value;
}
#Override
public EPersonType getPersonType() {
return EPersonType.Mother;
}
}
The main class
public class entryPointForTestingSerialize {
public static void main(String[] args) {
List<IPerson> family = new ArrayList<IPerson>();
IPerson father = new Father();
father.setAge(50);
father.setName("Oz");
father.setValue("Hello");
IPerson mother = new Mother();
mother.setAge(50);
mother.setName("Mother");
mother.setValue(false);
family.add(father);
family.add(mother);
String serialized = new JSONSerializer().deepSerialize(family);
System.out.println(serialized);
List<IPerson> deserialized = (List<IPerson>) new flexjson.JSONDeserializer<List<IPerson>>()
.use("values", new TypeLocator<String>("personType")
.add("Mother", Mother.class).add("Father", Father.class))
.deserialize(serialized);
System.out.println(deserialized);
}
}
The output
[{"age":50,"class":"testSerizlizeDeserializeInterface.Father","name":"Oz","personType":"Father","value":"Hello"},{"age":50,"class":"testSerizlizeDeserializeInterface.Mother","name":"Mother","personType":"Mother","value":false}]
Thanks!
Ozrad.

I solved it by changing the infrastructure to a better one, from my perspective. Its name is XStream and it handled everything smoothly and quickly. These lines of code, and it was all done:
XStream xstream = new XStream(new DomDriver()); // does not require XPP3 library
String xml = xstream.toXML(family);
and to get the data back:
List<IPerson> familyAfterSerialize = (List<IPerson>)xstream.fromXML(xml);

create a class to model a list

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);
}
}