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Problem with adjusting health in Pokemon class

I have two classes called Pokemon.java and Move.java which contain methods for creating and modifying Pokemon and their moves. I've created all of the required methods, but I'm having trouble with the attack method, which is supposed to subtract an opponent's health when it's attacked.
Here is the code for the Pokemon.java class:
import java.util.ArrayList;
public class Pokemon
{
// Copy over your code for the Pokemon class here
// Private constants
private static final int MAX_HEALTH = 100;
private static final int MAX_MOVES = 4;
private String name;
private int health;
private int opponentHealth;
public static int numMovesForPokemon = Move.getNumOfMoves();
private Move move;
private static ArrayList<Move> moveListForPokemon = new ArrayList<Move>();
private String pokemonImage;
// Write your Pokemon class here
public Pokemon(String theName, int theHealth)
{
name = theName;
if(theHealth <= MAX_HEALTH)
{
health = theHealth;
}
}
public Pokemon(String name, String image)
{
this.name = name;
health = 100;
pokemonImage = image;
}
public Pokemon(String theName)
{
name = theName;
}
public void setImage(String image)
{
pokemonImage = image;
}
public String getImage()
{
return pokemonImage;
}
public String getName()
{
return name;
}
public int getHealth()
{
return health;
}
public boolean hasFainted()
{
if(health <= 0)
{
return true;
}
else
{
return false;
}
}
public boolean canLearnMoreMoves()
{
if(numMovesForPokemon < 4)
{
return true;
}
else
{
return false;
}
}
public boolean learnMove(Move other)
{
if(canLearnMoreMoves())
{
moveListForPokemon = Move.getList();
moveListForPokemon.add(other);
numMovesForPokemon++;
return true;
}
else
{
return false;
}
}
public void forgetMove(Move other)
{
moveListForPokemon.remove(other);
}
public static ArrayList<Move> displayList()
{
return moveListForPokemon;
}
public boolean knowsMove(Move move)
{
if(moveListForPokemon.contains(move))
{
return true;
}
else
{
return false;
}
}
public boolean knowsMove(String moveName)
{
if(moveListForPokemon.contains(move.getName()))
{
return true;
}
else
{
return false;
}
}
public boolean attack(Pokemon opponent, Move move)
{
if(knowsMove(move))
{
opponentHealth = opponent.getHealth();
opponentHealth -= move.getDamage();
return true;
}
else
{
return false;
}
}
public boolean attack(Pokemon opponent, String moveName)
{
if(knowsMove(moveName))
{
opponentHealth = opponent.getHealth();
opponentHealth -= move.getDamage();
return true;
}
else
{
return false;
}
}
public String toString()
{
return pokemonImage + "\n" + name + " (Health: " + health + " / " + MAX_HEALTH + ")";
}
// Add the methods specified in the exercise description
}
Here is the code for the Move.java class:
import java.util.ArrayList;
public class Move
{
// Copy over your code for the Move class here
private static final int MAX_DAMAGE = 25;
private String name;
private int damage;
public static int numMoves;
private static ArrayList<Move> moveList = new ArrayList<Move>();
public Move(String theName, int theDamage)
{
name = theName;
if(theDamage <= MAX_DAMAGE)
{
damage = theDamage;
}
}
public String getName()
{
return name;
}
public int getDamage()
{
return damage;
}
public static int getNumOfMoves()
{
return numMoves;
}
public static ArrayList<Move> getList()
{
return moveList;
}
public String toString()
{
return name + " (" + damage + " damage)";
}
// Add an equals method so we can compare Moves against each other
public boolean equals(Move other)
{
if(name.equals(other.getName()))
{
return true;
}
else
{
return false;
}
}
}
Finally, here is the code for PokemonTester.java where I test out the methods:
public class PokemonTester extends ConsoleProgram
{
private PokemonImages images = new PokemonImages();
public void run()
{
// Test out your Pokemon class here!
Pokemon p1 = new Pokemon("Charrizard", 100);
Pokemon p2 = new Pokemon("Pikachu", 100);
Move m1 = new Move("Flamethrower", 20);
Move m2 = new Move("Fire Breath", 15);
p1.learnMove(m1);
System.out.println(p1.knowsMove(m1));
System.out.println(p1.knowsMove("Flamethrower"));
System.out.println(p1.attack(p2, m1));
System.out.println(p2.getHealth());
}
}

I suppose your problem is this:
opponentHealth = opponent.getHealth();
opponentHealth -= move.getDamage();
This code has several problems:
I'd suggest using a local variable for opponentHealth instead of a class level field
The opponent doesn't gets to know that it's health was subtracted. You have to share this knowledge with him, e.g. by introducing a setter for health and then calling opponent.setHealth(opponentHealth)

You are first assigning the value of Oponent.getHealth() to the int variable oponentHealth which you then modify, however this modification does not affect the health of Opponent but instead just the oponentHealth variable, you either have to directly access and modify the health field of Opponent or implement some kind of setHealth(int health) method in the class Pokemon

RPG game code error [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 5 years ago.
I keep getting this error in my code. Can someone fix it and how is the code written? Can it be improved by maybe using setters and getters only?
Exception in thread "main" java.lang.NullPointerException
at Player.attack(Player.java:72)
at Main.main(Main.java:15)
My code:
Player.java
public class Player {
String name;
String race;
int hp;
int power;
int armour;
Weapon weapon;
public Player (String n, String r, int h, int p, int a) {
name = n;
race =r;
hp = h;
power = p;
armour = a;
}
public void setName (String n) {
name = n;
}
public String getName() {
return name;
}
public void setRace (String r) {
race = r;
}
public String getRace() {
return race;
}
public void setHP (int h) {
hp = h;
}
public int getHP() {
return hp;
}
public void setPower (int p) {
power = p;
}
public int getPower() {
return power;
}
public void setArmour (int a) {
armour = a;
}
public int getArmour() {
return armour;
}
public boolean dead() {
return hp <= 0;
}
public boolean equip(Weapon weapon) {
this.weapon = weapon;
return true;
}
public boolean receiveDamage(int i) {
if ((hp - i) > 0) {
hp = hp - i;
return true;
}
hp = 0;
return false;
}
public boolean attack(Player player) {
return player.receiveDamage(weapon.useWeapon());
}
}
Main.java
public class Main {
public static void main(String args[]) {
Player Mensch = new Player("Mensch", "Mensch", 85, 12, 10);
Player Ork = new Player("Shrek", "Ork", 50, 14, 6);
Weapon MenschW = new Weapon("mächtiges Schwert", 15, 100);
Weapon OrkW = new Weapon("große Axt", 7, 100);
Mensch.equip(Mensch.weapon);
Ork.equip(Ork.weapon);
while (!Mensch.dead() && !Ork.dead() ) { //Alternativ: for (player hp >=0)
System.out.println("Mensch gegen Ork " + Mensch.attack(Ork));
if (Mensch.dead() || Ork.dead()) {
break;
}
System.out.println("Mensch gegen Ork " + Ork.attack(Mensch));
}
System.out.println("Ork ist tot: " + Ork.dead());
System.out.println("Mensch ist tot: " + Mensch.dead());
}
}
Weapon.java
import java.util.concurrent.ThreadLocalRandom;
public class Weapon {
String name;
int damage;
int hp;
public Weapon(String string, int d, int hp) {
// TODO Auto-generated constructor stub
}
public void setName (String n) {
name = n;
}
public String getName() {
return name;
}
public void setDamage (int d) {
damage = d;
}
public int getDamage() {
return damage;
}
public void setWHP (int h) {
hp = h;
}
public int getWHP() {
return hp;
}
public int useWeapon() {
if
(broken())
return 0;
hp = hp - 5;
return (damage / 2) + random();
}
private int random() {
return ThreadLocalRandom.current().nextInt(1, damage + 1);
}
private boolean broken() {
return hp <= 0;
}
}
I know its a lot of code but I keep getting the same error, also I'm quite new to java so I would appreciate some tips or suggestions to make my code better or more failsave. The code doesn't do much yet but it will (hopefully) be a simple game soon in which two characters fight eachother with some calculations on damageoutput of each player. In this case a Human and Ork. Feel free to try it out

Change
Mensch.equip(Mensch.weapon); // Mensch.weapon is not initialized in constructor so it is null.
Ork.equip(Ork.weapon); // Ork.weapon is not initialized in constructor so it is null as well.
To
// Use your newly created weapons in the main instead.
Mensch.equip(MenschW );
Ork.equip(OrkW);

using Adjacency list structure for directed graph java

I have problem to implement the transpose of a graph using only Adjacency List, without Edge List. Every vertex of the graph has a positional list that stores adjacent vertexes. When you have to transpose the graph, every element stored in a list of a vertex A, has to be removed and used as a source vertex. So if we have the situation
A -> B
B after its removal, add to its own adjacent list the old source Vertex A
We have as result:
B -> A
when I update the lists, i override the last information stored in, so I lose connection between vertexes.
public class Vertice implements Comparable<Vertice>{
public Vertice(int valore){
this.valore = valore;
this.color = Color.WHITE;
this.distanza = 0;
this.padre = null;
adiacenze = new NodePositionList<Vertice>();
}
public int getValore() {
return valore;
}
public void setValore(int valore) {
this.valore = valore;
}
public Color getColor() {
return color;
}
public void setColor(Color color) {
this.color = color;
}
public Position<Vertice> getPadre() {
return padre;
}
public void setPadre(Position<Vertice> padre) {
this.padre = padre;
}
public int getDistanza() {
return distanza;
}
public void setDistanza(int distanza) {
this.distanza = distanza;
}
public enum Color{
BLACK, WHITE, GREY;
}
public String toString(){
StringBuilder sb = new StringBuilder();
sb.append("v_" + valore );
return sb.toString();
}
public boolean equals(Vertice v){
return this.compareTo(v) == 0;
}
#Override
public int compareTo(Vertice o) {
return this.valore - o.getValore();
}
public int getFin() {
return fin;
}
public void setFin(int fin) {
this.fin = fin;
}
public Position<Vertice> getRiferimentoVertice() {
return riferimentoVertice;
}
public void setRiferimentoVertice(Position<Vertice> riferimentoVertice) {
this.riferimentoVertice = riferimentoVertice;
}
public Iterable<Vertice> getAdiacenze() {
return adiacenze;
}
public void setAdiacenze(NodePositionList<Vertice> adiacenze) {
this.adiacenze = adiacenze;
}
public Position<Vertice> addNodoAdiacente(Vertice v){
Position<Vertice> newVertice = adiacenze.addLast(v);
v.setRiferimentoAsAdiacenza(newVertice);
return newVertice;
}
public Position<Vertice> removeNodoAdiacente(Position<Vertice> v){
return adiacenze.remove(v);
}
public Position<Vertice> getRiferimentoAsAdiacenza() {
return riferimentoAsAdiacenza;
}
public void setRiferimentoAsAdiacenza(Position<Vertice> riferimentoAsAdiacenza) {
this.riferimentoAsAdiacenza = riferimentoAsAdiacenza;
}
public boolean hasAdiacent(){
return adiacenze.size() == 0;
}
public boolean hasRedEdge(){
return redEdge;
}
public void setHasRedEdge(boolean redEdge){
this.redEdge = redEdge;
}
private boolean redEdge;
private int valore;
private Color color;
private Position<Vertice> padre;
private int distanza;
private int fin;
private Position<Vertice> riferimentoVertice;
private Position<Vertice> riferimentoAsAdiacenza;
private NodePositionList<Vertice> adiacenze;
here the "Grafo.java" class
public class Grafo {
public Grafo(int numV){
verticiGrafo = new NodePositionList<Vertice>();
listaArchi = new NodePositionList<Arco>();
this.V = numV;
}
public Position<Vertice> addVertice(Vertice v){
Position<Vertice> newAdded = verticiGrafo.addLast(v);
v.setRiferimentoVertice(newAdded);
return newAdded;
}
public NodePositionList<Vertice> getVertici(){
return verticiGrafo;
}
public Position<Arco> addArco(Arco a){
a.getSorgente().element().addNodoAdiacente(a.getDestinazione().element());
Position<Arco> newAdded = listaArchi.addLast(a);
a.setRiferimentoArco(newAdded);
return newAdded;
}
public Position<Arco> connect(Position<Vertice> sorgente, Position<Vertice> destinazione){
Arco a = new Arco(sorgente, destinazione);
Vertice v_sorgente = sorgente.element();
Vertice v_destinazione = destinazione.element();
v_sorgente.addNodoAdiacente(v_destinazione);
Position<Arco> newAdded = listaArchi.addLast(a);
a.setRiferimentoArco(newAdded);
return newAdded;
}
public Position<Arco> removeArco(Position<Arco> a){
a.element().getSorgente().element().removeNodoAdiacente(a.element().getDestinazione());
return listaArchi.remove(a);
}
public Iterable<Arco> archi(){
return listaArchi;
}
public void invertiArco(Position<Arco> a){
Arco a1 = a.element();
Position<Vertice> temp = a1.getDestinazione();
a1.setDestinazione(a1.getSorgente());
a1.setSorgente(temp);
Vertice sorgente = a1.getSorgente().element();
Vertice destinatario = a1.getDestinazione().element();
sorgente.addNodoAdiacente(destinatario);
}
public Position<Arco> getArcoByVertici(Position<Vertice> sorgente, Position<Vertice> destinazione){
for(Arco a: listaArchi){
if(a.getColor() == EdgeColor.NONE){
Vertice dest = a.getDestinazione().element();
Vertice sorg = a.getSorgente().element();
if(sorg.equals(sorgente.element()) && dest.equals(destinazione.element())){
return a.getRiferimentoArco();
}
}
}
return null;
}
public void removeAllAdiacenze(){
for(Vertice v: this.getVertici()){
v.setAdiacenze( new NodePositionList<Vertice>());
}
}
public void setColorArco(Position<Arco> a, EdgeColor ec){
a.element().setColor(ec);
}
public NodePositionList<Arco> getListaArchi() {
return listaArchi;
}
public void setListaArchi(NodePositionList<Arco> listaArchi) {
this.listaArchi = listaArchi;
}
private NodePositionList<Vertice> verticiGrafo;
private NodePositionList<Arco> listaArchi; //lista archi uscenti
public final int V;
}
here the method on the "Ricerca.java" class that I'm trying to make
public static Grafo traspostaGrafo(Grafo g){
NodePositionList<Vertice> npl = g.getVertici();
Position<Vertice> u = npl.first();
while (u != npl.getTail()){
u.element().setColor(Color.WHITE);
NodePositionList<Vertice> adiacenti = g.getListaAdiacenti(u.element().getValore());
Position<Vertice> adiacente = adiacenti.first();
while (adiacente != adiacenti.getTail() && adiacente.element().getFlag() == 0){
g.addNodoAdiacente(adiacente.element(), u.element());
g.removeNodoAdiacente(adiacente);
adiacente = adiacenti.next(adiacente);
u.element().setFlag(1);
}
}
return g
}

Rideable Controllable Entity minecraft

I am having a problem making an entity controllable in minecraft. I am are able to mount it, and it will move, but a few seconds after you move it, it just jumps back to where it was before you moved it. Here is my Entity class:
package net.minecraft.src;
public class mod_EntityMech extends EntityMob // this to make mob hostile
{
public boolean stationary;
public mod_EntityMech(World par1World)
{
super(par1World);
isImmuneToFire = false;
}
public int func_82193_c(Entity par1Entity) //the amount of damage
{
return 4;
}
protected void fall(float par1)
{}
public int getMaxHealth() // Mob health
{
return 1000;
}
protected int getDropItemId()
{
return 0;
}
protected boolean canDespawn()
{
return false;
}
public boolean interact(EntityPlayer entityplayer)
{
if (riddenByEntity == null || riddenByEntity == entityplayer)
{
entityplayer.mountEntity(this);
return true;
}
else
{
return false;
}
}
protected boolean isMovementCeased()
{
return stationary;
}
public void moveEntity(double d, double d1, double d2)
{
if (riddenByEntity != null)
{
this.prevRotationYaw = this.rotationYaw = this.riddenByEntity.rotationYaw;
this.rotationPitch = this.riddenByEntity.rotationPitch * 0.5F;
this.setRotation(this.rotationYaw, this.rotationPitch);
this.rotationYawHead = this.renderYawOffset = this.rotationYaw;
stationary = true;
motionX += riddenByEntity.motionX * 10; // * 0.20000000000000001D;
motionZ += riddenByEntity.motionZ * 10; // * 0.20000000000000001D;
if (isCollidedHorizontally)
{
isJumping = true;
}
else
{
isJumping = false;
}
super.moveEntity(motionX, motionY, motionZ);
}
else
{
stationary = false;
super.moveEntity(d, d1, d2);
}
}
public void onUpdate()
{
super.onUpdate();
if (riddenByEntity != null) //check if there is a rider
{
//currentTarget = this;
this.randomYawVelocity = 0; //try not to let the horse control where to look.
this.rotationYaw = riddenByEntity.rotationYaw;
}
}
protected boolean isAIEnabled() //Allow your AI task to work?
{
return true;
}
}
P.S. I am using ModLoader

You need to add client-server-sync by using message-handling. I recommend using this tutorial: http://www.minecraftforge.net/forum/index.php/topic,20138.0.html

Java LinkedList with Object

Trying to implement a LinkedList that simulates a Portfolio, consisting of Stock objects. I'm struggling to figure out how to properly iterate through the list and check if each stock contains certain parameters. the SHAREPRICE method is the one I'm having trouble with specifically, if someone could help with that, I'd be very grateful. What I have so far:
import java.util.*;
public class Portfolio<AnyType> implements Iterable<AnyType> {
public int balance, shares;
private Stock<AnyType> beginMarker, endMarker, temp;
LinkedList<Stock> Portfolio = new LinkedList<Stock>();
java.util.Iterator<Stock> iter = Portfolio.iterator();
public int CASHIN(int x) {
balance = x;
return balance;
}
public int CASHOUT(int y) {
balance = balance + (-y);
return balance;
}
public int CASHBALANCE() {
return balance;
}
public void BUY(String t, int s, float pp) {
temp = new Stock<AnyType>(t, s, pp, pp, 0, null, null);
Portfolio.add(temp);
shares = shares + s;
}
public void SELL(String t, int s, float pp) {
shares = shares - s;
}
public void SHAREPRICE(String t, float pp)
{
if(Portfolio.contains(Stock.)
{
}
}
public void QUERY(String t) {
}
public int COUNTPORTFOLIO() {
return shares;
}
public void PRINTPORTFOLIO() {
}
public java.util.Iterator<AnyType> iterator() {
return new Iterator();
}
private class Iterator implements java.util.Iterator<AnyType> {
private Stock<AnyType> current = beginMarker.next;
private boolean okToRemove = false;
public boolean hasNext() {
return current != endMarker;
}
public AnyType next() {
if (!hasNext())
throw new java.util.NoSuchElementException();
AnyType nextItem = (AnyType) current.getTicker();
current = current.next;
okToRemove = true;
return nextItem;
}
public void remove() {
if (!okToRemove)
throw new IllegalStateException();
Portfolio.this.remove(current.prev);
okToRemove = false;
}
}
private class Stock<AnyType> implements Comparable<Stock<AnyType>> {
public String getTicker() {
return ticker;
}
public void setTicker(String ticker) {
this.ticker = ticker;
}
public float getPurchasePrice() {
return purchasePrice;
}
public void setPurchasePrice(float purchasePrice) {
this.purchasePrice = purchasePrice;
}
public float getLatestPrice() {
return latestPrice;
}
public void setLatestPrice(float latestPrice) {
this.latestPrice = latestPrice;
}
public float getPctChange() {
return pctChange;
}
String ticker;
int sharesOwned;
float purchasePrice, latestPrice;
float pctChange = (latestPrice - purchasePrice) / purchasePrice;
Stock<AnyType> prev, next;
public Stock(String ticker, int sharesOwned, float purchasePrice,
float latestPrice, float pctChange, Stock<AnyType> prev,
Stock<AnyType> next) {
this.ticker = ticker;
this.sharesOwned = sharesOwned;
this.purchasePrice = purchasePrice;
this.latestPrice = latestPrice;
this.pctChange = pctChange;
this.prev = prev;
this.next = next;
}
public int compareTo(Stock<AnyType> pctChange) {
return ((Comparable) this.pctChange)
.compareTo(Stock.getPctChange());
}
}
}
class TestPortfolio {
public static void main(String[] args) {
}
}

Forward Direction:
while(itr.hasNext())
{
System.out.println(itr.next());
}
Reverse Direction
while(itr.hasPrevious())
System.out.println(itr.previous());
}