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Looking for an implementation of an abstract method

I need to make a programm which is like a rally, theres 2 types of vehicles, motorcycle and cars, two types of motorcycle, with and without sidecar, the thing is that I need to verify if there is just a motorcycle in an array list, I mean, two wheels vehicle. That verification should be done in a method called esDe2Ruedas(), which is called by an abstract overrided method called check() that should be the one that verifies if a group of vehicles from an array are able to run in the rally, if its true all the elements of the array must be from the same type.
Here is the code
this is how the program arrays the vehicles
GrandPrix gp1 = new GrandPrix();
gp1.agregar(v1);
//gp1.mostrar(v1);
gp1.agregar(v2);
System.out.println(gp1.check());
GrandPrix gp2 = new GrandPrix();
gp2.agregar(vt1);
gp2.agregar(vt2);
gp2.agregar(m2);
System.out.println(gp2.check());
GrandPrix gp3 = new GrandPrix();
gp3.agregar(vt1);
gp3.agregar(vt2);
gp3.agregar(m1);
System.out.println(gp3.check());
GrandPrix gp4 = new GrandPrix();
gp4.agregar(m1);
gp4.agregar(m2);
System.out.println(gp4.check());
This is the class that is using
import java.util.ArrayList;
public class GrandPrix extends Rally{
ArrayList<Vehiculo> ve = new ArrayList<Vehiculo>();
public void agregar(Vehiculo v) {
ve.add(v);
}
public void agregar(Carro c) {
ve.add(c);
}
public void agregar(Moto m) {
ve.add(m);
}
#Override
boolean check() {// HERE I VERIFY IF THE VEHICLES ARE COMPATIBLE
return false;
}
}
This is the class where everything goes on
public class Vehiculo {
private String Nombre;
private double velocidad_max;
private int peso;
private int comb;
public Vehiculo() {
setNombre("Anónimo");
setVel(130);
setPeso(1000);
setComb(0);
}
public Vehiculo(String string, double d, int i, int j) {
setNombre(string);
setVel(d);
setPeso(i);
setComb(j);
}
double rendimiento() {
return velocidad_max/peso;
}
public boolean mejor(Vehiculo otroVehiculo) {
return rendimiento()>otroVehiculo.rendimiento();
}
public String toString() {
return getNombre()+"-> Velocidad máxima = "+getVel()+" km/h, Peso = "+getPeso()+" kg";
}
/**************************************
---------SET And GET Nombre------------
***************************************/
public String getNombre() {
return Nombre;
}
public void setNombre(String nuevoNombre) {
this.Nombre=nuevoNombre;
}
/**************************************
---------SET And GET velocidad_max------------
***************************************/
public double getVel() {
return velocidad_max;
}
public void setVel(double nuevaVel) {
this.velocidad_max=nuevaVel;
}
/**************************************
---------SET And GET peso------------
***************************************/
public double getPeso() {
return peso;
}
public void setPeso(int nuevoPeso) {
this.peso=nuevoPeso;
}
/**************************************
---------SET And GET comb------------
***************************************/
public int getComb() {
return comb;
}
public void setComb(int comb) {
this.comb = comb;
}
boolean esDe2Ruedas() {
return false;
}
}
This is the class of motorcycles, which is in theory the same as the car's class, without sidecar thing
public class Moto extends Vehiculo{
private boolean sidecar;
public Moto(String string, double d, int i, int j) {
setNombre(string);
setVel(d);
setPeso(i);
setComb(j);
setSidecar(false);
}
public Moto(String string, double d, int i, int j, boolean b) {
setNombre(string);
setVel(d);
setPeso(i);
setComb(j);
setSidecar(b);
esDe2Ruedas(false);
}
public String toString() {
String str = null;
if(isSidecar())
str =super.toString()+", Moto, con sidecar";
else
str =super.toString()+", Moto";
return str;
}
public boolean isSidecar() {
return sidecar;
}
public void setSidecar(boolean sidecar) {
this.sidecar = sidecar;
}

I guess what you presented is what is given. If you came up with the design it is ok, but I believe it could be improved. Anyway, I try to respond to what I believe was your question straight away.
Vehiculo is the super type of Moto (which can have a side car and becomes 3 wheeler).
Vehiculo has a method esDe2Ruedas, which returns false.
Moto inherits that method <-- this is wrong, it should override it and, depending on side car, return the expected boolean value.
In the check method you can now distinguish between Moto and "Moto with sidecar" by using that method.

Populating array in sub class with parent class getter java

Sorry as I know this is obvious but I cant figure it out!
I have a parent class named 'Set', representing a set of a tennis match.
public class Set {
private String set1;
private String set2;
private String set3;
//private Object[] match;
public Set() {
setSet1(set1);
setSet2(set2);
setSet3(set3);
}
public void setSet1(String set1) {
this.set1 = set1;
}
public String getSet1() {
return set1;
}
public void setSet2(String set2) {
this.set2 = set2;
}
public String getSet2() {
return set2;
}
public void setSet3(String set3) {
this.set3 = set3;
}
public String getSet3() {
return set3;
}
public String toString(){
return String.format("set1: %s, set2: %s, set3: %s", set1, set2, set3);
}
}
And a sub class of 'Set' named 'SingleSet', where i try to add the sets into an array named 'game':
public class SingleSet extends Set{
private Object homePlayer;
private Object awayPlayer;
private String[] game;
public SingleSet(Object homePlayer, Object awayPlayer){
super();
game = new String[3];
game[0] = super.getSet1();
game[1] = super.getSet2();
game[2] = super.getSet3();
setHomePlayer(homePlayer);
setAwayPlayer(awayPlayer);
}
public void setHomePlayer(Object homePlayer) {
this.homePlayer = homePlayer;
}
public Object getHomePlayer() {
return homePlayer;
}
public void setAwayPlayer(Object awayPlayer) {
this.awayPlayer = awayPlayer;
}
public Object getAwayPlayer() {
return awayPlayer;
}
public void setGame(String[] game) {
this.game = game;
}
public String[] getGame() {
return game;
}
public String toString(){
return String.format("Player: %s Vs. Player: %s, Single set game: %s, %s, %s", homePlayer, awayPlayer, game[0], game[1], game[2]);
}
}
And this is where I am trying to add the Sets from my parents class into my sub class (this is for FXML, so the code is in my controller):
public void submit() {
SingleSet game1 = new SingleSet(homePlayer1Dropdown.getValue(), awayPlayer1Dropdown.getValue());
game1.setSet1(set1Box1.getText());
game1.setSet2(set1Box2.getText());
game1.setSet3(set1Box3.getText());
System.out.println(game1);
When I print the result, all my values are null. I tried printing them individually and that worked fine, so I know the 'set1Box.getText()' is working fine.
Again sorry for any obvious rookie error!
I've updated my code and same issue. Thank you for the composition answer, I will need it for my project, but this is a IS-A relationship

Make sure that the toString() methods of the following attributes exist and return a correct string.
It seems as if there is no way to get a String from homePlayer, awayPlayer and all indices of game[x].
public String toString(){
return String.format("Player: %s Vs. Player: %s, Single set game: %s, %s, %s", homePlayer, awayPlayer, game[0], game[1], game[2]);
}

Missing return statement method ReturnCopy

I've created this method and I'm unsure why it says there's a missing return statement. do I need to change the print to a return? (it's the method at the very bottom) I'm a bit of a Java beginner so any help will be appreciated!
public class Book {
private String title;
private String author;
private int copies;
private boolean borrowed;
public Book( String inAuthor, String inTitle, int inNumberOfCopies ) {
this.author = inAuthor;
this.title = inAuthor;
this.copies = inNumberOfCopies;
}
public void borrowed() {
borrowed = true;
}
public void rented() {
borrowed = true;
}
public void returned() {
borrowed = false;
}
public boolean isBorrowed() {
return borrowed;
}
public String getAuthor() {
return this.author;
}
public static String getTitle() {
return getTitle();
}
public int getTotalCopies() {
return this.copies;
}
public int getAvailableCopies() {
}
public void withdrawCopy() {
int found = 0;
for (Book b : Library.getListOfBooks()) {
if (b.getTitle().equals(title)) {
if (found == 0) {
found = 1;
}
if (!b.isBorrowed()) {
b.borrowed=true;
found = 2;
break;
}
if (found == 0) {
System.out.println("Sorry, this book is not in our catalog.");
} else if (found == 1) {
System.out.println("Sorry, this book is already borrowed.");
} else if (found == 2) {
System.out.println("You successfully borrowed " + title);
}
}
}
}
public String returnCopy() {
boolean found = false;
for (Book book : Library.getListOfBooks()) {
if (getTitle().equals(title) && book.isBorrowed()) {
book.returned();
found = true;
}
if (found) {
System.out.println("you successfully returned " + title);
}
}
}
}

public String returnCopy()
String after public means that this method will return a String.
Your public String returnCopy() is currently not returning anything.
If you don't want to return anything, you can use void like this:
public void returnCopy(){
// code
}
Same issue with public int getAvailableCopies(), this is supposed to return an int but you are not returning anything.
Be careful:
this method:
public static String getTitle() {
return getTitle();
}
is a recursive method without a base condition. This will cause an error and force your application to crash.

You've defined the method as returning a String but you don't return a value anywhere in the method body. Simplest fix is probably to change the return type to void...
public void returnCopy() {...
}

All the above answer are pointing to the same issue, you have defined methods that are breaking the contract about what they return..
In you code you have as well something like this:
public int getAvailableCopies() {
}
so you are telling the compiler, you have a method with the name getAvailableCopies, it takes no params and return an integer.
BUT if you don't return anything, then you are contradicting your own method, your own contract, this is an enough reason for a compiler to complain...
Conclusion:
keep in mind the information that defines the method.

Overriding value in heap java programming

I've added to my project a new data structure Heap<Integer,Integer> but the only problem I've got is that it prints me only one time the result.
If I have the input:
v=10;new(v,20);new(a,22);print(v)
at the end of execution
Heap={1->20, 2->22},
SymTable={v->1, a->2}
But what it gives me:
Heap: 1->22
SymTable: a -> 1
v -> 1
It overrides the first value.Here is the code from the controller where is the main part:
HeapAllocation crtStmt1=(HeapAllocation) crtStmt;
String varI = crtStmt1.getVarname();
Exp e = crtStmt1.getExpression();
int i=0;
Id<Object,Integer> tbl = state.getDict();
IHeap<Integer,Integer> heap1 = state.getHeap();
int value= e.eval(tbl, heap1);
heap1.put(++i, value);
if (tbl.containsKey(varI))
tbl.update(varI,i);
tbl.update(varI, i);
The problem I guess is after this line:
heap1.put(++i, value);
because for a new operation it doesn't append to the previous one, just overrides it.
Edit:
The implementation of the heap:
public class Heap<Integer,In> implements IHeap<Integer, Integer>,Serializable{
private Map<Integer, Integer> mapp;
public Heap(){
mapp = new HashMap<Integer,Integer>();
}
public void put(Integer index, Integer value){
mapp.put(index, value);
}
public void remove(Integer index){
try{
if(isEmpty())
throw new ExceptionRepo();
else
mapp.remove(index);
}catch (ExceptionRepo ex){
System.err.println("Error: Heap is empty.");
}
}
public boolean isEmpty(){
return mapp.isEmpty();
}
public Integer get(Integer index){
return mapp.get(index);
}
public boolean containsIndex(Integer index){
return mapp.containsKey(index);
}
public void update(Integer index, Integer value){
mapp.put(index, value);
}
public String toString(){
Set<Integer> all = mapp.keySet();
Object[] keysA= all.toArray();
String res="";
for(int i=0; i<mapp.size(); i++){
Integer v = mapp.get(keysA[i]);
res += keysA[i].toString() + "->" + v.toString() + "\r\n";
}
return res;
}
}
Edit2: Maybe the problem is in the eval function implementation.To be clear, I have a Exp class:
public class Exp{
public int eval(Id<Object,Integer> tbl)throws ExceptionRepo{
return 0;
}
public String toString(){
return "";
}
public int eval(Id<Object,Integer> tbl,IHeap<Integer,Integer> heap) throws ExceptionRepo{
return 0;
}
And some derived classes that extends the Exp class.I added a new method in the ConstExp class:
public class ConstExp extends Exp implements Serializable{
int number;
public int eval(Id<Object,Integer> tbl) throws ExceptionRepo{
return number;
}
public ConstExp(int n){
number = n;
}
public String toString(){
return "" + number;
}
public int eval(Id<Object,Integer> tbl,IHeap<Integer,Integer> heap) throws ExceptionRepo{
return number; //THIS IS THE NEW METHOD
}
This class should return a value..so for "v=20", after execution of the statement it puts the value 20 in the v based on this class implementation.
If it's useful this is the statement evaluation rule for the heap(that I implemented in the controller up there):
Stack1={new(var,exp)| Stmt2|...}
SymTable1
Heap1
==>
Stack2={Stmt2|...}
let be v=eval(exp,SymTable1,Heap1) in
Heap2 = Heap1 U {newfreelocation ->v}
if var exists in SymTable1 then SymTable2 = update(SymTable1,
var,newfreelocation)
else SymTable2 = add(SymTable1,var, newfreelocation)
How to resolve this?

Java ArrayList.contains() & add() method

So I'm having this problem with adding an element to an ArrayList
I have a class Media with 3 fields and another class Mediatheque with 1 field(which is an ArrayList).
Let's say I have:
A Mediatheque media = new Mediatheque
An equals(Media m) method in class Media < (important method)
I need to write a method add(Media m) which:
If the media.contenu does contain an element equals to the Media m I want to add, I must NOT add it and increase the nbEx field of the element contained in media.contenu
-Else I can add it using the add method provided by the ArrayList ( This doesn't seem too hard)
So I tried to write a contains(Media) method which uses the equals(Media m) method I wrote for the Media class and then use the contains method in the add method.
My question is that how am I supposed to write the add method? < (The Question)
I must write this using ArrayList, it is a school assignment
Sorry about the long code and the bad English, I'm a complete noob.
Here is my Media class:
package Ex1;
public class Media {
private final String support; // Format: Book, CD, DVD,etc...
private final String titre; // Title
private int nbEx; // Number of copy
public Media(String titre, String support){
this.titre = titre;
this.support = support;
this.nbEx = 1;
}
public Media (){
titre = "";
support = "";
nbEx = 0;
}
public boolean equals(Media m){
boolean equality = false;
if (m instanceof Media){
equality = (this.titre.equals(m.titre) && this.support.equals(m.support));
}
return equality;
}
public Media(Media m){
this.titre = m.titre;
this.support = m.support;
}
}
And here is my Mediatheque class:
import java.util.ArrayList;
import static java.lang.System.out;
public class Mediatheque {
ArrayList<Media> contenu;
public Mediatheque(){
this.contenu = new ArrayList<Media>();
}
public Mediatheque(Mediatheque m){
this.contenu = m.contenu;
}
public boolean contains(Media m){
int i = 0;
boolean contain = this.contenu.get(i).equals(m);
for(i = 0; i<this.contenu.size(); i++){
if(contain)
break;
}
return contain;
}
public int indexOf(Media m){
boolean retVal = this.contenu.get(i).equals(m);
for(Media i : contenu){
if(contain)
break;
}
return i;
}
public void add(Media m){
if(this.contains(m)){
this.contenu.get(this.contenu.indexOf(m)).setNbEx(this.contenu.get(this.contenu.indexOf(m)).getNbEx()+m.getNbEx());
}else{
this.contenu.add(m);
}
}
My question is that how am I supposed to write the add method?
Sorry about the long code and the bad English, I'm a complete noob.
Thank you!

As stated by #NeplatnyUdaj in the comment of your question, the use of a Map would greatly improve your code. Instead of recording the number of medias inside the Media object, use a HashMap<Media, Integer> to store your data in this way:
new HashMap<Media, Integer> map = new HashMap<Media,Integer>();
if ( map.containsKey(key) ) {
map.put(key, (map.get(key) + 1));
} else {
map.put(key, 1);
}
Where key is the media. (m in your code)

When one overrides the equals() method, one is also supposed to override the hashCode() method. The equals() method takes an Object parameter. Here's how your Media class should look like:
// Media.java
public class Media
{
private final String support;
private final String title;
public Media(String title, String support)
{
this.title = title;
this.support = support;
}
public Media(Media media)
{
this(media.title, media.support);
}
#Override
public int hashCode()
{
return 31 * title.hashCode() + support.hashCode();
}
#Override
public boolean equals(Object object)
{
if (object instanceof Media)
{
Media media = (Media) object;
return media.title.equals(title) &&
media.support.equals(support);
}
return false;
}
}
Then use a HashMap to map the media with its number of copies. Here's how that's done:
// MediaMap.java
import java.util.HashMap;
import java.util.Map;
public class MediaMap
{
// Media to its Number of Copies mapping.
private Map<Media, Integer> mediaMap;
public MediaMap()
{
mediaMap = new HashMap<>();
}
public void add(Media media)
{
mediaMap.put(media, mediaMap.getOrDefault(media, 0) + 1);
}
public void removeOneMedia(Media media)
{
if (mediaMap.containsKey(media))
{
mediaMap.put(media, mediaMap.get(media) - 1);
}
}
// And so on...
}
Without overriding the hashCode() method in the Media class, the hash based collections won't work as expected.
You can also have a look at MultiSet data structure, and use that instead.
If you are to use ArrayList then here's how its done:
// Media.java
public class Media
{
private final String support;
private final String title;
private int numberOfCopies;
public Media(Media media)
{
this(media.title, media.support, media.numberOfCopies);
}
public Media(String title, String support, int numberOfCopies)
{
this.title = title;
this.support = support;
this.numberOfCopies = numberOfCopies;
}
#Override
public int hashCode()
{
return 31 * title.hashCode() + support.hashCode();
}
#Override
public boolean equals(Object object)
{
if (object instanceof Media)
{
Media media = (Media) object;
return media.title.equals(title) &&
media.support.equals(support);
}
return false;
}
public int getNumberOfCopies()
{
return numberOfCopies;
}
public void setNumberOfCopies(int numberOfCopies)
{
this.numberOfCopies = numberOfCopies;
}
}
And here's a MediaList class which uses ArrayList:
// MediaList.java
import java.util.ArrayList;
public class MediaList
{
private ArrayList<Media> mediaList;
public MediaList()
{
mediaList = new ArrayList<>();
}
public void add(Media media)
{
set(media, +1);
}
public void remove(Media media)
{
set(media, -1);
}
private void set(Media media, int change)
{
if (change == 0)
{
return;
}
int indexOfMedia = mediaList.indexOf(media);
if (indexOfMedia != -1)
{
Media m = mediaList.get(indexOfMedia);
m.setNumberOfCopies(m.getNumberOfCopies() + change);
if (change < 0 && m.getNumberOfCopies() <= 0)
{
mediaList.remove(media);
}
}
else if (change > 0)
{
mediaList.add(media);
}
}
// And so on...
}

I have refactored your classes a little bit. I also implemented an add method. I assumed that you want to add media to the mediatheque if it is not already in the list. If it is in the list you want to add the nbex to the nbex that the item in the list has, right?
As the others I would advise you to use a HashMap() for counting if you don't need the number for your media objects.
Media.class
public class Media {
private final String support; // Format: Book, CD, DVD,etc...
private final String titre; // Title
private int nbEx; // Number of copy
public Media(String titre, String support){
this.titre = titre;
this.support = support;
this.nbEx = 1;
}
public Media(Media m){
this(m.titre, m.support);
}
public Media (){
this("", "");
nbEx = 0;
}
public boolean equals(Media m){
if (m instanceof Media){
return (this.titre.equals(m.titre) && this.support.equals(m.support));
}
return false;
}
}
Mediatheque.class
public class Mediatheque {
ArrayList<Media> contenu;
public Mediatheque(){
this.contenu = new ArrayList<Media>();
}
public Mediatheque(Mediatheque m){
this.contenu = m.contenu;
}
public boolean contains(Media m){
for(Media media: this.contenu) {
if(media.equals(m) {
return true;
}
}
return false;
}
public int indexOf(Media m){
if(this.contenu.contains(m) {
return this.contenu.indexOf(m);
}
return -1;
}
public void add(Media m){
if(this.contains(m)) {
Media media = this.contenu.get(this.contenu.indexOf(m));
media.setNbex(media.getNbex() + m.getNbex());
} else {
this.contenu.add(m);
}
}
}
Hope this helps.