I get stack overflow error when I try to load(). I am trying to read PhoneBookEntry objects from a txt file. The txt file has a name and number which make up the PhoneBookEntry object.
Can you please let me know what I'm doing wrong?
package HashSet;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Scanner;
public class PhoneBook {
int capacity = 10;
private ArrayList<PhoneBookEntry>[] buckets;
public PhoneBook() {
this(10);
}
public PhoneBook(int size) {
capacity = size;
buckets = new ArrayList[size];
for (int i = 0; i < buckets.length; i++) {
buckets[i] = new ArrayList<PhoneBookEntry>();
}
}
public int getSize() {
int tot = 0;
for (ArrayList<PhoneBookEntry> x : buckets)
tot += x.size();
return tot;
}
public boolean add(PhoneBookEntry entry) {
if (contains(entry))
return false;
int x = Math.abs(entry.hashCode());
buckets[x % buckets.length].add(entry);
return true;
}
public void load()
{
InputStream is = getClass().getClassLoader().getResourceAsStream("phone.txt");
Scanner scan = new Scanner(is);
if (scan.hasNext())
add(new PhoneBookEntry(scan.next());
}
public void bucketSize() {
for (int i = 0; i < buckets.length; i++)
System.out.println(i + " " + buckets[i].size());
}
public boolean contains(PhoneBookEntry word) {
int x = Math.abs(word.hashCode());
return buckets[x % buckets.length].contains(word);
}
public int getCapacity() {
return capacity;
}
public static void main(String[] args) {
PhoneBook phone = new PhoneBook();
phone.load();
}
}
package HashSet;
import java.util.LinkedList;
import java.util.ListIterator;
public class PhoneBookEntry {
String n;
Integer nr;
LinkedList<PhoneBookEntry> list;
public PhoneBookEntry(String name, int number) {
list = new LinkedList<PhoneBookEntry>();
n = name;
nr = number;
list.add(new PhoneBookEntry(n, nr));
}
public String getN() {
return n;
}
public void setN(String n) {
this.n = n;
}
public Integer getNr() {
return nr;
}
#Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((n == null) ? 0 : n.hashCode());
result = prime * result + ((nr == null) ? 0 : nr.hashCode());
return result;
}
#Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
PhoneBookEntry other = (PhoneBookEntry) obj;
if (n == null) {
if (other.n != null)
return false;
} else if (!n.equals(other.n))
return false;
if (nr == null) {
if (other.nr != null)
return false;
} else if (!nr.equals(other.nr))
return false;
return true;
}
public void setNr(Integer nr) {
this.nr = nr;
}
#Override
public String toString() {
return n + " " + nr;
}
}
Every new phone book entry creates a new phone book entry that creates a new phone book entry that creates a new phome book entry, etc... ad infinitum. That is, until the stack space runs out.
You need to rethink your application data structure.
public PhoneBookEntry(String name, int number) {
list = new LinkedList<PhoneBookEntry>();
n = name;
nr = number;
list.add(new PhoneBookEntry(n, nr));
}
is causing an infinite recursion. You likely need a new class to put in the linked list (PhoneNumber or some such if a PhoneBookEntry can contain multiple names/numbers, otherwise ditch it.)
Related
I've topped with a problem I can not understand exactly what's happening here.
I operate with a TreeMap<Custom_class, TreeMap<Custom_class, Integer>>
Here is the fragment of code:
TreeMap<Coordenada, Integer> helper_tree;
boolean newLine = false;
for (Linea l : this.lineas) {
int helper = 0;
newLine = true;
Coordenada helper_co = null;
for (Coordenada c : l.getNodosLinea()) {
helper++;
if (!c.getEsEstacion() && !c.getEsCruce()) continue;
if (newLine) { map.putIfAbsent(c, new TreeMap<>()); helper_co = c; helper = 0; newLine = false; continue; }
helper_tree = new TreeMap<>();
helper_tree.put(helper_co, helper * 200);
map.put(c, helper_tree);
map.get(helper_co).put(c, helper * 200);
helper_co = c;
helper = 0;
}
}
In the execution the highlighted line fails, getting 0 entry for a key:
debug mode in intellij
And this is TreeMap structure:
TreeMap structure
I dont understand why in fails at .get(key) when the key Coordenada(12,2) is present. All before works just fine.
Coordenada class
public class Coordenada implements Comparable<Coordenada>{
private int[] coordenada = new int[2];
private boolean esEstacion = false;
private boolean esCruce = false;
public Coordenada(int[] coordenada){
this.coordenada[0] = coordenada[0];
this.coordenada[1] = coordenada[1];
}
public void setCoordenada(int[] coordenada) {
this.coordenada = coordenada;
}
public int[] getCoordenada() {
return coordenada;
}
public void switchEstacion(){
this.esEstacion = !this.esEstacion;
}
public void switchCruce() { this.esCruce = !this.esCruce; }
public boolean getEsEstacion() {
return this.esEstacion;
}
public boolean getEsCruce() { return this.esCruce; }
#Override
public boolean equals(Object coord){
Coordenada coordTemp = (Coordenada) coord;
if (this.coordenada[0] != coordTemp.coordenada[0])
return false;
if (this.coordenada[1] != coordTemp.coordenada[1])
return false;
return true;
}
#Override
public int compareTo(Coordenada o) {
if (this.coordenada[0] > o.coordenada[0] )
return 1;
if (this.coordenada[1] > o.coordenada[1] )
return 1;
if (this.coordenada[0] < o.coordenada[0])
return -1;
if (this.coordenada[1] < o.coordenada[1])
return -1;
return 0;
}
#Override
public String toString() {
return "(" + coordenada[0] + ", " + coordenada[1] + ")";
}
}
Inserts perfectly Coordenada(12,2) and modifies previous helper_co = Coordenada(10,2)
debugger variables
Thanks for any help!
Look at your compareTo function
(0,1) compareTo (1,0) returns 1
(1,0) compareTo (0,1) returns 1
It's ambiguous.
I have been following a tutorial I found. It is however in C++ and I'm using Java so there might have been a few things lost in translation. I've tried both googling and searching here and while there seem to be plenty of asked questions I still remain stuck. Though it feels like I'm very close.
According to the tutorial, there should be a match for the pattern 'nan' but there simply is no match when I'm running it. What am I missing? Sorry for code that unformated itself when pasted.
package u1;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Arrays;
import java.util.Scanner;
public class SuffixSort {
public Element[] processPattern(String pattern) {
Element[] patternArray = new Element[pattern.length()];
for (int i = 0; i < pattern.length(); i++) {
patternArray[i] = new Element(i, pattern.substring(i, pattern.length()));
}
Arrays.sort(patternArray);
return patternArray;
}
public void binarySearch(String text, String pattern, Element[] array) {
int left = 0, right = text.length() - 1;
int mid = 0, result;
while (left <= right) {
mid = left + (right - left) / 2;
result = pattern.compareTo(array[mid].getSuffix());
if (result == 0) {
System.out.println("Match: " + array[mid].getIndex());
return;
} else if (result < 0) {
right = mid - 1;
} else {
left = mid + 1;
}
}
}
public static void main(String[] args) {
try {
String text = "banana";
String pattern = "nan";
SuffixSort ss = new SuffixSort();
Scanner in = new Scanner(new FileReader("src/resources/100k.txt"));
/*
* while (in.hasNextLine()) { text += in.nextLine(); }
*/
Element[] suffixArray = ss.processPattern(text);
double runtime = System.nanoTime();
ss.binarySearch(text, pattern, suffixArray);
runtime = (System.nanoTime() - runtime) / 1000000;
in.close();
System.out.println(runtime);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}
Other class
package u1;
public class Element implements Comparable<Element>{
private int index;
private String suffix;
public Element(int index, String suffix){
this.index = index;
this.suffix = suffix;
}
#Override
public int compareTo(Element o) {
return this.getSuffix().compareTo(o.getSuffix());
}
public int getIndex() {
return index;
}
public String getSuffix() {
return suffix;
}
public void setSuffix(String suffix) {
this.suffix = suffix;
}
}
I'm using Eclipse and I'm using Java. My objective it's to sort a vector, with the bogoSort method
in one vector( vectorExample ) adapted to my type of vector and use the Java sort on other vector (javaVector) and compare them.
I did the tests but it did't work, so I don't know what is failing.
*Note: there are few words in spanish: ordenado = sorted, Ejemplo = Example, maximo = maximun, contenido = content.
EjemploVector class
package vector;
import java.util.NoSuchElementException;
import java.util.Vector;
import java.util.Iterator;
public class EjemploVector <T> {
protected T[] contenido;
private int numeroElementos;
#SuppressWarnings("unchecked")
public EjemploVector () {
contenido = (T[]) new Object[100];
numeroElementos = 0;
}
#SuppressWarnings("unchecked")
public EjemploVector (int maximo) {
contenido = (T[]) new Object[maximo];
numeroElementos = 0;
}
public String toString(){
String toString="[";
for (int k=0; k<numeroElementos;k++){
if (k==numeroElementos-1){
toString = toString + contenido[k].toString();
} else {
toString = toString + contenido[k].toString()+", ";
}
}
toString = toString + "]";
return toString;
}
public boolean equals (Object derecho){
if (!(derecho instanceof Vector<?>)) {
return false;
} else if (numeroElementos != ((Vector<?>)derecho).size()) {
return false;
} else {
Iterator<?> elemento = ((Vector<?>)derecho).iterator();
for (int k=0; k<numeroElementos;k++){
if (!((contenido[k]).equals (elemento.next()))) {
return false;
}
}
return true;
}
}
public void addElement (T elemento){
contenido[numeroElementos++]= elemento;
}
protected T[] getContenido(){
return this.contenido;
}
protected T getContenido (int k){
return this.contenido[k];
}
#SuppressWarnings("unchecked")
protected void setContenido (int k, Object elemento){
this.contenido[k]= (T)elemento;
}
EjemploVectorOrdenadoClass
package vector.ordenado;
import java.util.Arrays;
import java.util.Random;
import vector.EjemploVector;
public class EjemploVectorOrdenado<T extends Comparable<T>> extends EjemploVector<T> {
private boolean organized;
public EjemploVectorOrdenado() {
super();
organized = true;
}
public EjemploVectorOrdenado(int maximo) {
super(maximo);
organized = true; //
}
public boolean getOrdenado() {
return this.organized;
}
// Method bogoSort
public void bogoSort() {
if (!this.organized) {
if (this.size() > 0) {
Random generator;
T tempVariable;
int randomPosition;
do {
generator = new Random();
for (int i = 0; i < this.size(); i++) {
randomPosition = generator.nextInt(this.size());
tempVariable = contenido[i];
contenido[i] = contenido[randomPosition];
contenido[randomPosition] = tempVariable;
}
} while (!organized);
}
}
this.organized = true;
}
public void addElement(T elemento) {
super.addElement(elemento);
if (organized && this.size() > 1) {
T penultimo = this.getContenido(this.size() - 2);
T ultimo = this.getContenido(this.size() - 1);
organized = penultimo.compareTo(ultimo) <= 0;
}
}
}
ElementoTest class
package elementos;
import java.io.Serializable;
public class ElementoTest implements Comparable<ElementoTest>, Serializable {
private static final long serialVersionUID = -7683744298261205956L;
private static int numeroElementosTest = 0;
private int clave;
private int valor;
public ElementoTest(int i){
this.clave = i;
this.valor = numeroElementosTest;
numeroElementosTest++;
}
public String toString(){
return ("(" + this.clave + "," + this.valor + ")");
}
public boolean equals (Object derecho){
if (!(derecho instanceof ElementoTest)) {
return false;
} else {
return clave == ((ElementoTest)derecho).clave;
}
}
public char getClave(){
return this.clave;
}
public int getValor(){
return this.valor;
}
#Override
public int compareTo(ElementoTest elemento) {
if (elemento == null){
return -1;
} else if (this.equals(elemento)){
return 0;
} else if (clave < elemento.clave){
return -1;
} else {
return 1;
}
}
}
TESTS
The first it's a stupid test, because it puts elements in order so... really the methods aren´t doing anything, java just compare and it gives correct
I tried to make an unsorted vector adding elements but there appears the java.lang.ClassCastException: [Ljava.... etc.
package vector.ordenado;
import static org.junit.Assert.*;
import java.util.Collections;
import java.util.Vector;
import org.junit.Before;
import org.junit.Test;
import elementos.ElementoTest;
public class EjemploVectorOrdenadoTest {
private Vector<ElementoTest> vectorJava;
private EjemploVectorOrdenado<ElementoTest> vectorExample;
#Before
public void setUp() throws Exception {
vectorJava = new Vector<ElementoTest>(100);
vectorExample = new EjemploVectorOrdenado<ElementoTest>(100);
}
#Test
public void testSortFailTest() {
for (char c = 'a'; c < 'g'; c++) {
vectorJava.addElement(new ElementoTest(c));
vectorExample.addElement(new ElementoTest(c));
}
Collections.sort(vectorJava);
vectorExample.bogoSort();
assertTrue(vectorExample.equals(vectorJava));
assertTrue(vectorExample.getOrdenado());
}
#Test
public void testSort() {
{
vectorJava.addElement(new ElementoTest(1));
vectorJava.addElement(new ElementoTest(3));
vectorJava.addElement(new ElementoTest(2));
vectorExample.addElement(new ElementoTest(3));
vectorExample.addElement(new ElementoTest(2));
vectorExample.addElement(new ElementoTest(1));
}
Collections.sort(vectorJava);
vectorExample.bogoSort();
assertTrue(vectorExample.equals(vectorJava));
assertTrue(vectorExample.getOrdenado());
}
}
Sorry, for the problems and thanks.
The problem is that your test class ElementoTest should implement the Comparable interface. Or you need to provide a Comparator during your comparison.
Does your class ElementtoTest implement Comparable?
If not, it needs to.
I'm suspecting it doesn't, because that's exactly what would cause this error. you'll need to add implements Comparable and then override the int compareTo(Elementtotest e) method, where you specify what criteria you'd like to order the objects based on.
my issue is in my "NumberAnalyzer.java" class, I'm supposed to be able to use the "Number.java" class to determine if a number from the ArrayList is odd (as well as even and perfect later on) but since the "isOdd()" method in "Number.java" doesn't read in an int or other variable itself, I can't find a way to test each number to make "oddCount" in the "countOdds" method of "NumberAnalyzer.java" increase to produce the number of odd numbers in the string from the runner class.
NumberAnalyzer.java
import java.util.ArrayList;
import java.util.Scanner;
import com.sun.xml.internal.ws.api.pipe.NextAction;
import static java.lang.System.*;
public class NumberAnalyzer
{
private ArrayList<Number> list;
public NumberAnalyzer()
{
}
public NumberAnalyzer(String numbers)
{
list = new ArrayList<Number>();
String nums = numbers;
Scanner chopper = new Scanner(nums);
while(chopper.hasNext()){
int num = chopper.nextInt();
list.add(new Number(num));
}
chopper.close();
System.out.println(list);
}
public void setList(String numbers)
{
list = new ArrayList<Number>();
String nums = numbers;
Scanner chopper = new Scanner(nums);
while(chopper.hasNext()){
int num = chopper.nextInt();
list.add(new Number(num));
}
chopper.close();
}
public int countOdds()
{
int oddCount=0;
for(int i = 0; i < list.size(); i++){
if(Number.isOdd()== true){
oddCount++;
}
}
return oddCount;
}
public int countEvens()
{
int evenCount=0;
return evenCount;
}
public int countPerfects()
{
int perfectCount=0;
return perfectCount;
}
public String toString( )
{
return "";
}
}
Number.java
public class Number
{
private Integer number;
public Number()
{
}
public Number(int num)
{
number = num;
}
public void setNumber(int num)
{
number = num;
}
public int getNumber()
{
return number;
}
public boolean isOdd()
{
if(number%2==0){
return false;
}
return true;
}
public boolean isPerfect()
{
int total=0;
for(int i = 1; i < number; i++){
if(number%i==0){
total+= i;
}
}
return (number==total);
}
public String toString( )
{
String output = getNumber() + "\n" + getNumber()+ "isOdd == " + isOdd() + "\n" + getNumber()+ "isPerfect==" + isPerfect()+ "\n\n";
return output;
}
}
runner class
import java.util.ArrayList;
import java.util.Scanner;
import static java.lang.System.*;
public class Lab16b
{
public static void main( String args[] )
{
NumberAnalyzer test = new NumberAnalyzer("5 12 9 6 1 4 8 6");
out.println(test);
out.println("odd count = "+test.countOdds());
out.println("even count = "+test.countEvens());
out.println("perfect count = "+test.countPerfects()+"\n\n\n");
//add more test cases
}
}
When you call
test.countOdds());
control goes to NumberAnalyzer.java
public int countOdds()
{
int oddCount=0;
for(int i = 0; i < list.size(); i++){
if(Number.isOdd()== true){
oddCount++;
}
}
return oddCount;
}
And here you are calling Number.isOdd() method by Class name as a static way but i do not think you can do this way because isOdd() is not static.
It is compile time error
Solution:
Iterate your list and send value one by one from the list to isOdd(int val) method.
Try to make isOdd() method static which accept one numeric parameter and will return true or false.
increase your counter based on return type as you do.
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.