public class PlaneDemo
{
public static void main(String args[])
{
ArrayQueue<Plane> q = new ArrayQueue<Plane>();
Plane p1 = new Plane("Aircraft 1", 3);
Plane p2 = new Plane("Aircraft 2", 1);
Plane p3 = new Plane("Aircraft 3", 2);
q.addQueue(p1);
q.addQueue(p2);
q.addQueue(p3);
while(!q.isEmptyQueue())
{
System.out.println("Vehicle: ");
System.out.println(q.front());
q.deleteQueue();
}
}
}
cannot find symbol
q.addQueue(p1);
^
symbol: method addQueue(Plane)
location: variable q of type ArrayQueue<Plane>
error: cannot find symbol
q.addQueue(p2);
^
symbol: method addQueue(Plane)
location: variable q of type ArrayQueue<Plane>
Im like panicking this is due soon and I can't figure out what I did wrong.
public class ArrayQueue<T>
{
private int maxQueueSize;
private int count;
private int queueFront;
private int queueRear;
private T[] list;
public ArrayQueue()
{
maxQueueSize = 100;
queueFront = 0;
queueRear = maxQueueSize - 1;
count = 0;
list = (T[]) new Object[maxQueueSize];
}
public ArrayQueue(int queueSize)
{
if(queueSize <= 0)
{
System.err.println("Array size must be a positive number. Creating array at default size of 100.");
maxQueueSize = 100;
}
else
maxQueueSize = queueSize;
queueFront = 0;
queueRear = maxQueueSize - 1;
count = 0;
list = (T[]) new Object[maxQueueSize];
}
public void initializeQueue()
{
for(int i = queueFront; i < queueRear; i = (i + 1) % maxQueueSize)
list[i] = null;
queueFront = 0;
queueRear = maxQueueSize - 1;
count = 0;
}
public boolean isEmptyQueue()
{
return(count == 0);
}
public boolean isFullQueue()
{
return(count == maxQueueSize);
}
public T peek() //throws QueueUnderflowException
{
/*if(isEmptyQueue())
throw new QueueUnderflowException();*/
return (T) list[queueFront];
}
/*public T back() throws QueueOverflowException
{
if(isFullQueue())
throw new QueueUnderflowException();
return (T) list[queueRear];
}
*/
public void enqueue(T queueElement) throws QueueOverflowException
{
if(isFullQueue())
throw new QueueOverflowException();
queueRear = (queueRear + 1) % maxQueueSize;
count++;
list[queueRear] = queueElement;
}
public void dequeue() throws QueueUnderflowException
{
if(isEmptyQueue())
throw new QueueUnderflowException();
count--;
list[queueFront] = null;
queueFront = (queueFront + 1) % maxQueueSize;
}
}
Replace this
q.addQueue(p1);
q.addQueue(p2);
q.addQueue(p3);
For this q.enqueue(p1); etc because is the only,method you have to add an element to the class
public void enqueue(T queueElement) throws QueueOverflowException
{
Related
everybody
I have some questions~
In the main method , int size = s.getSize()
but when I change to int size = s.size()
Why compiler show NoSuchMethodError?
Mystack is a ArrayList's child class
Why can't I use size() method?
package ch11;
import java.util.ArrayList;
import java.util.Scanner;
public class ch11_10 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
MyStack s = getStack(input);
int size = s.getSize();//換成s.size()
for (int i = 0; i < size; i++) {
System.out.println(s.pop());
}
}
public static MyStack getStack(Scanner input) {
System.out.print("Enter five strings: ");
MyStack s = new MyStack();
for (int i = 0; i < 5; i++) {
s.push(input.next());
}
return s;
}
}
class MyStack extends ArrayList {
public int getSize() {
return size();
}
public Object peek() {
return get(size() - 1);
}
public Object pop() {
Object o = get(size() - 1);
remove(size() - 1);
return o;
}
public void push(Object o) {
add(o);
}
#Override
public String toString() {
return "stack: " + toString();
}
}
I've written my first Genetic Algorithm in Java and I'm able to optimize functions with one argument x, but I don't know how to optimize functions with two arguments x and y. Algorithm class and main app works correctly so i send only Individual.java and Population.java. If I think correctly in genes I have only x-coordinate but I'm not sure how to add y-coordinate. Any advise will be helpfull.
Individual.java
public class Individual {
private int[] genes;
private int fitness;
private Random randomGenerator;
public Individual() {
this.genes = new int[Constants.CHROMOSOME_LENGTH];
this.randomGenerator = new Random();
}
public void generateIndividual() {
for(int i = 0; i < Constants.CHROMOSOME_LENGTH; i++) {
int gene = randomGenerator.nextInt(2);
genes[i] = gene;
}
}
public double f(double x) {
// return Math.pow(x,2);
return (Math.pow((1-x),2)) + (100*(Math.pow((1-Math.pow(x,2)),2)));
// return Math.sin(x)*((x-2)*(x-2))+3;
}
public double getFitness() {
double genesToDouble = genesToDouble();
return f(genesToDouble);
}
public double getFitnessResult() {
double genesToDouble = genesToDouble();
return genesToDouble;
}
public double genesToDouble() {
int base = 1;
double geneInDouble = 0;
for( int i =0; i < Constants.GENE_LENGTH; i++) {
if(this.genes[i] == 1)
geneInDouble += base;
base = base*2;
}
geneInDouble = (geneInDouble / 1024) * 10.1;
return geneInDouble;
}
public int getGene(int index) {
return this.genes[index];
}
public void setGene(int index, int value) {
this.genes[index] = value;
this.fitness = 0;
}
}
Population.java
public class Population {
private Individual[] individuals;
public Population(int populationSize) {
individuals = new Individual[populationSize];
}
public void initialize() {
for(int i = 0; i < individuals.length; i++) {
Individual newIndividual = new Individual();
newIndividual.generateIndividual();
saveIndividual(i, newIndividual);
}
}
public Individual getIndividual(int index) {
return this.individuals[index];
}
//maksimum lub minimum
public Individual getFittestIndividual() {
Individual fittest = individuals[0];
for(int i =0; i < individuals.length; i++) {
if(getIndividual(i).getFitness() < fittest.getFitness())
fittest = getIndividual(i);
}
return fittest;
}
public int size() {
return this.individuals.length;
}
public void saveIndividual(int index, Individual individual) {
this.individuals[index] = individual;
}
}
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 4 years ago.
This program cannot run but I don't know why:
Abstract class
public class Mahasiswa implements Comparable {
private String nama;
private int nim;
public Mahasiswa(String nama, int nim) {
}
public String getNama() {
return nama;
}
public int getNim() {
return nim;
}
public void setNama() {
this.nama=nama;
}
public void setNim() {
this.nim=nim;
}
#Override
public int compareTo(Object o) {
Mahasiswa key = (Mahasiswa) o;
if (this.nama.compareTo(key.getNama()) == 0) {
return -1;
}else if (this.nama.compareTo(key.getNama()) > 0) {
return 1;
}else{
return 0;
}
}
}
Method class:
public static Mahasiswa[] BubbleSort(Object[] object) {
Mahasiswa[] data =(Mahasiswa[]) object;
for (int i = 1; i < data.length; i++) {
for (int j = 0; j < data.length - i; j++) {
if (((Comparable)data[j]).compareTo(data[j+1]) ==1 ) {
Mahasiswa c = data[j];
data[j] = data[j + 1];
data[j + 1] = c;
}
}
}
return data;
}
Main class
public class Main {
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
Mahasiswa[] data = {new Mahasiswa("Karel", 175314105),
new Mahasiswa("Fandur", 175314006),
new Mahasiswa("Yeski", 1753141104),
new Mahasiswa("Tiosu", 175314001),
new Mahasiswa("Jono", 175314090)};
Larik.BubbleSort(data);
for (int i = 0; i < data.length; i++) {
System.out.println(data[i].getNama()+" "+data[i].getNim());
}
}
}
Output
Exception in thread "main" java.lang.NullPointerException
at SortingObject.Mahasiswa.compareTo(Mahasiswa.java:33)
at SortingObject.Larik.BubbleSort(Larik.java:16)
at SortingObject.Main.main(Main.java:24)
C:\Users\Yeski's Legion\AppData\Local\NetBeans\Cache\8.2\executor-
snippets\run.xml:53: Java returned: 1
BUILD FAILED (total time: 0 seconds)
You have to set the instance variable value either constructor or setter, otherwise it will be null.
public Mahasiswa(String nama, int nim) {
this.nama = nama;
this.nim = nim;
}
You can also use setter methods.
I have already made a posting about this program once, but I am once again stuck on a new concept that I am learning (Also as a side note; I am a CS student so please DO NOT simply hand me a solution, for my University has strict code copying rules, thank you.). There are a couple of difficulties I am having with this concept, the main one being that I am having a hard time implementing it to my purposes, despite the textbook examples making perfect sense. So just a quick explanation of what I'm doing:
I have an entity class that takes a Scanner from a driver. My other class then hands off the scanner to a superclass and its two subclasses then inherit that scanner. Each class has different data from the .txt the Scanner read through. Then those three classes send off their data to the entity to do final calculations. And that is where my problem lies, after all the data has been read. I have a method that displays a new output along with a few methods that add data from the super along with its derived classes.EDIT: I simply cannot figure out how to call the instance variable of my subclasses through the super so I can add and calculate the data.
Here are my four classes in the order; Driver, Entity, Super, Subs:
public static final String INPUT_FILE = "baseballTeam.txt";
public static void main(String[] args) {
BaseballTeam team = new BaseballTeam();
Scanner inFile = null;
try {
inFile = new Scanner(new File(INPUT_FILE));
team.loadTeam(inFile);
team.outputTeam();
} catch (FileNotFoundException e) {
System.out.println("File " + INPUT_FILE + " Not Found.");
System.exit(1);
}
}
}
public class BaseballTeam {
private String name;
private Player[] roster = new Player[25];
Player pitcher = new Pitcher();
Player batter = new Batter();
BaseballTeam() {
name = "";
}
public String getName() {
return name;
}
public void setName(String aName) {
name = aName;
}
public void loadTeam(Scanner input) {
name = input.nextLine();
for (int i = 0; i < roster.length; i++) {
if (i <= 9) {
roster[i] = new Pitcher();
}
else if ((i > 9) && (i <= 19)) {
roster[i] = new Batter();
}
else if (i > 19) {
roster[i] = new Player();
}
roster[i].loadData(input);
roster[i].generateDisplayString();
//System.out.println(roster[i].generateDisplayString()); //used sout to test for correct data
}
}
public void outputTeam() {
if ((pitcher instanceof Player) && (batter instanceof Player)) {
for (int i = 0; i < roster.length; i++) {
System.out.println(roster[i].generateDisplayString());
}
}
//How do I go about doing calculates?
public int calculateTeamWins() {
if ((pitcher instanceof ) && (batter instanceof Batter)) {
}
return 0;
}
public int calculateTeamSaves() {
if ((pitcher instanceof Pitcher) && (batter instanceof Batter)) {
}
return 0;
}
public double calculateTeamERA() {
if ((pitcher instanceof Pitcher) && (batter instanceof Batter)) {
}
return 0;
}
public double calculateTeamWHIP() {
if ((pitcher instanceof Pitcher) && (batter instanceof Batter)) {
}
return 0;
}
public double calculateTeamBattingAverage() {
if ((pitcher instanceof Pitcher) && (batter instanceof Batter)) {
}
return 0;
}
public int calculateTeamHomeRuns() {
if ((pitcher instanceof Pitcher) && (batter instanceof Batter)) {
}
return 0;
}
public int calculateTeamRBI() {
if ((pitcher instanceof Pitcher) && (batter instanceof Batter)) {
}
return 0;
}
public int calculateStolenBases() {
if ((pitcher instanceof Pitcher) && (batter instanceof Batter)) {
}
return 0;
}
}
public class Player {
protected String name;
protected String position;
Player(){
name = "";
position = "";
}
public String getName() {
return name;
}
public void setName(String aName) {
name = aName;
}
public String getPosition() {
return position;
}
public void setPosition(String aPosition) {
position = aPosition;
}
public void loadData(Scanner input){
do {
name = input.nextLine();
} while (name.equals(""));
position = input.next();
//System.out.println(generateDisplayString());
}
public String generateDisplayString(){
return "Name: " + name + ", Position:" + position;
}
}
public class Pitcher extends Player {
private int wins;
private int saves;
private int inningsPitched;
private int earnedRuns;
private int hits;
private int walks;
private double ERA;
private double WHIP;
Pitcher() {
super();
wins = 0;
saves = 0;
inningsPitched = 0;
earnedRuns = 0;
hits = 0;
walks = 0;
}
public int getWins() {
return wins;
}
public void setWins(int aWins) {
wins = aWins;
}
public int getSaves() {
return saves;
}
public void setSaves(int aSaves) {
saves = aSaves;
}
public int getInningsPitched() {
return inningsPitched;
}
public void setInningsPitched(int aInningsPitched) {
inningsPitched = aInningsPitched;
}
public int getEarnedRuns() {
return earnedRuns;
}
public void setEarnedRuns(int aEarnedRuns) {
earnedRuns = aEarnedRuns;
}
public int getHits() {
return hits;
}
public void setHits(int aHits) {
hits = aHits;
}
public int getWalks() {
return walks;
}
public void setWalks(int aWalks) {
walks = aWalks;
}
#Override
public void loadData(Scanner input) {
super.loadData(input);
wins = input.nextInt();
saves = input.nextInt();
inningsPitched = input.nextInt();
earnedRuns = input.nextInt();
hits = input.nextInt();
walks = input.nextInt();
}
#Override
public String generateDisplayString() {
calculateERA();
calculateWHIP();
return String.format(super.generateDisplayString() + ", Wins:%1d, Saves:%1d,"
+ " ERA:%1.2f, WHIP:%1.3f ", wins, saves, ERA, WHIP);
}
public double calculateERA() {
try {
ERA = ((double)(earnedRuns * 9) / inningsPitched);
} catch (ArithmeticException e) {
ERA = 0;
}
return ERA;
}
public double calculateWHIP() {
try {
WHIP = ((double)(walks + hits) / inningsPitched);
} catch (ArithmeticException e) {
WHIP = 0;
}
return WHIP;
}
}
public class Batter extends Player {
private int atBats;
private int hits;
private int homeRuns;
private int rbi;
private int stolenBases;
private double batAvg;
Batter() {
super();
atBats = 0;
hits = 0;
homeRuns = 0;
rbi = 0;
stolenBases = 0;
}
public int getAtBats() {
return atBats;
}
public void setAtBats(int aAtBats) {
atBats = aAtBats;
}
public int getHits() {
return hits;
}
public void setHits(int aHits) {
hits = aHits;
}
public int getHomeRuns() {
return homeRuns;
}
public void setHomeRuns(int aHomeRuns) {
homeRuns = aHomeRuns;
}
public int getRbi() {
return rbi;
}
public void setRbi(int aRbi) {
rbi = aRbi;
}
public int getStolenBases() {
return stolenBases;
}
public void setStolenBases(int aStolenBases) {
stolenBases = aStolenBases;
}
#Override
public void loadData(Scanner input) {
super.loadData(input);
atBats = input.nextInt();
hits = input.nextInt();
homeRuns = input.nextInt();
rbi = input.nextInt();
stolenBases = input.nextInt();
}
#Override
public String generateDisplayString() {
calculateBattingAverage();
return String.format(super.generateDisplayString() +
", Batting Average:%1.3f, Home Runs:%1d, RBI:%1d, Stolen Bases:%1d"
, batAvg, homeRuns, rbi, stolenBases);
}
public double calculateBattingAverage() {
try{
batAvg = ((double)hits/atBats);
} catch (ArithmeticException e){
batAvg = 0;
}
return batAvg;
}
}
Also, its probably easy to tell I'm still fairly new here, because I just ran all my classes together in with the code sample and I can't figure out to add the gaps, so feel free to edit if need be.
The typical usage of instanceof in the type of scenario you're describing would be
if (foo instanceof FooSubclass) {
FooSubclass fooSub = (FooSubclass) foo;
//foo and fooSub now are references to the same object, and you can use fooSub to call methods on the subclass
} else if (foo instanceof OtherSubclass) {
OtherSubclass otherSub = (OtherSubclass) foo;
//you can now use otherSub to call subclass-specific methods on foo
}
This is called "casting" or "explicitly casting" foo to FooSubclass.
the concept to call the methods of your subclasses is called polymorphism.
In your runtime the most specific available method is called provided that the method names are the same.
so you can
Superclass class = new Subclass();
class.method();
and the method provided that overwrites the method in Superclass will be called, even if it's defined in the Subclass.
Sorry for my english, I hope that helps a little bit ;-)
I have three classes, those being Lister, ObjectSortedList and SortedListProgram. I'm having trouble with the iterator for the generic class. What am I doing wrong?
This is the error I get:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 6
at objectsortedlist.ObjectSortedList.getData(ObjectSortedList.java:122)
at objectsortedlist.Lister.hasNext(Lister.java:28)
at objectsortedlist.SortedListProgram.main(SortedListProgram.java:52)
Java Result: 1
Here are my classes:
package objectsortedlist;
import java.util.Iterator;
/**
*
* #author Steven
*/
public class ObjectSortedList<T> implements Cloneable, Iterable<T> {
private T[] data;
private int capacity;
public ObjectSortedList()
{
final int init_capacity = 10;
capacity = 0;
data = (T[])new Object[init_capacity];
}
public ObjectSortedList(int init_capacity)
{
if(init_capacity < 0)
throw new IllegalArgumentException("Initial capacity is negative: " + init_capacity);
capacity = 0;
data = (T[])new Object[init_capacity];
}
private boolean empty()
{
if(data.length == 0 || data[0] == null)
return true;
else
return false;
}
public int length()
{
return capacity;
}
public void insert(T element)
{
if(capacity == data.length)
{
ensureCapacity(capacity * 2 + 1);
}
data[capacity] = element;
capacity++;
}
public boolean delete(T target)
{
int index;
if(target == null)
{
index = 0;
while((index < capacity) && (data[index] != null))
index++;
}
else
{
index = 0;
while((index < capacity) && (!target.equals(data[index])))
index++;
}
if(index == capacity)
return false;
else
{
capacity--;
data[index] = data[capacity];
data[capacity] = null;
return true;
}
}
private void ensureCapacity(int minCapacity)
{
T[] placeholder;
if(data.length < minCapacity)
{
placeholder = (T[])new Object[minCapacity];
System.arraycopy(data, 0, placeholder, 0, capacity);
data = placeholder;
}
}
public ObjectSortedList<T> clone()
{
// Cloning
ObjectSortedList<T> answer;
try
{
answer = (ObjectSortedList<T>) super.clone();
}
catch(CloneNotSupportedException cnse)
{
throw new RuntimeException("This class does not implement cloneable.");
}
answer.data = data.clone();
return answer;
}
#Override
public Iterator<T> iterator()
{
return (Iterator<T>) new Lister<T>(this, 0);
}
public T getData(int index)
{
return (T)data[index];
}
}
package objectsortedlist;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
*
* #author Steven
*/
public class Lister<T> implements Iterator<T>
{
private ObjectSortedList<T> current;
private int index;
public Lister(ObjectSortedList<T> top, int index)
{
current = top;
this.index = index;
}
#Override
public boolean hasNext()
{
return (current.getData(index) == null);
}
#Override
public T next()
{
T answer;
if(!hasNext())
throw new NoSuchElementException("The Lister is empty.");
answer = current.getData(index+1);
return answer;
}
#Override
public void remove() {
throw new UnsupportedOperationException("Don't use this. Use objectsortedlist.SortedList.delete(T target).");
}
}
package objectsortedlist;
import java.util.Scanner;
/**
*
* #author Steven
*/
public class SortedListProgram {
private static Scanner scan = new Scanner(System.in);
private static String[] phraseArray = {"Hullabaloo!", "Jiggery pokery!", "Fantastic!", "Brilliant!", "Clever!", "Geronimo!", "Fish sticks and custard.", "Spoilers!",
"Exterminate!", "Delete!", "Wibbly-wobbly!", "Timey-wimey!"};
private static Lister<String> print;
public static void main(String args[])
{
int phraseNo = 0;
System.out.println("I'm gonna say some things at you, and you're going to like it."
+ " How many things would you like me to say to you? Put in an integer from 1-12, please.");
try
{
phraseNo = Integer.parseInt(scan.nextLine());
while((phraseNo < 1) || (phraseNo > 12))
{
System.out.println("The integer you entered wasn't between 1 and 12. Make it in between those numbers. Please? Pleaseeeee?");
phraseNo = Integer.parseInt(scan.nextLine());
}
}
catch(NumberFormatException nfe)
{
System.out.println("C'mon, why don't you follow directions?");
phraseNo = 0;
}
if(phraseNo == 0);
else
{
ObjectSortedList<String> phrases = new ObjectSortedList<String>(phraseNo);
for(int i = 0; i < phrases.length(); i++)
{
phrases.insert(phraseArray[i]);
}
print = new Lister<String>(phrases, phraseNo);
while(print.hasNext())
System.out.println(print.next());
}
}
}
After looking at your code I found multiple issues, here are they:
In your SortedListProgram class, in following code the phrases.length() will be 0, so the it will never go in that loop.
ObjectSortedList<String> phrases = new ObjectSortedList<String>(phraseNo);
for(int i = 0; i < phrases.length(); i++)
{
phrases.insert(phraseArray[i]);
}
Moreover in SortedListProgram class's this call sequence
print.hasNext() -> current.getData(index)
the index passed is equal to size of data array field in the
ObjectSortedList class and Since in java array indexes ranges from
zero to array size -1. So you are bound to get
java.lang.ArrayIndexOutOfBoundsException always.
Please correct your code.