I've run into the java.lang.NullPointerException error and would appreciate information on how to go about fixing the error. I understand that it's having an issue with something being null but I cannot figure out what.
Basically, the issue only began to occur once I tried to put together a Do-While loop. If I remove the loop and edit the code so as to only run once when the method getHistogram() has been called the error does not occur.
Here is some of my code to get a look at what i'm doing as of right now and where the error occurs. What can I do to stop this error from happening?
Page 1.
public class MainClass {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int optionSelected;
int NumberOfSuits;
int NumberOfRanks;
int numberOfCardsDealt = 0;
int SizeOfDeck;
int numberOfCards;
System.out.printf( "How many suits? " );
NumberOfSuits = getDecision();
System.out.printf( "How many ranks? " );
NumberOfRanks = getDecision();
SizeOfDeck = NumberOfSuits * NumberOfRanks;
DeckofCards newDeck = new DeckofCards();
newDeck.setDeckofCards(NumberOfRanks, NumberOfSuits);
newDeck.createDeckofCards();
do {
System.out.println ( newDeck.toString() );
System.out.printf ( "1=Shuffle, 2=Deal 1 Hand, 3= Deal 100000 Times,"
+ "4=Quit: " );
optionSelected = getDecision();
switch ( optionSelected ) {
case 1:
newDeck.shuffleDeckofCards();
break;
case 2:
numberOfCards = getCardDecision();
numberOfCardsDealt = numberOfCardsDealt + numberOfCards;
if ( SizeOfDeck > numberOfCardsDealt ) {
String[] dealCards = newDeck.dealCards ( numberOfCards );
for ( String printCardsDealt : dealCards ) {
System.out.println ( printCardsDealt );
}
}
else {
System.out.println ( "Deck must be re-shuffled" );
numberOfCardsDealt = 0;
break;
}
break;
case 3:
numberOfCards = getCardDecision();
int[] histogram = newDeck.getHistogram( numberOfCards );
for ( int printHistogram : histogram ) {
System.out.println ( printHistogram );
}
break;
}
} while ( optionSelected != 4 );
}
public static int getDecision() {
String numberMatch;
int optionSelected = 0;
Scanner in = new Scanner(System.in);
do {
numberMatch = in.next();
if( numberMatch.matches("[0-9]+" ) ){
optionSelected = Integer.parseInt( numberMatch );
}
if ( optionSelected < 1 || optionSelected > 9 ){
System.out.println("Try again!");
}
} while ( optionSelected < 1 || optionSelected > 9 );
return optionSelected;
}
public static int getCardDecision() {
String numberMatch;
int optionSelected = 0;
Scanner in = new Scanner(System.in);
do {
System.out.printf ( "How many cards? " );
numberMatch = in.next();
if( numberMatch.matches("[0-9]+" ) ){
optionSelected = Integer.parseInt( numberMatch );
}
if ( optionSelected < 1 || optionSelected > 9 ){
System.out.println("Try again!");
}
} while ( optionSelected < 1 || optionSelected > 9 );
return optionSelected;
}
}
Page 2.
public class DeckofCards {
private int NumberOfRanks;
private int NumberOfSuits;
private int SizeOfDeck;
private String newDeck[];
private String dealThisDeck[];
private int howManyCards;
private int cardsDealtTotal = 0;
private int numberOfCardsDealt;
private int numberOfCards;
private String dealtDeck[];
private int CardsDealtInTotal = 0;
private int histoSum[];
public void setDeckofCards ( int NumberOfRanks, int NumberOfSuits ) {
this.NumberOfRanks = NumberOfRanks;
this.NumberOfSuits = NumberOfSuits;
}
public void createDeckofCards() {
SizeOfDeck = NumberOfRanks * NumberOfSuits;
Cards newCard = new Cards();
newCard.setCards ( NumberOfRanks, NumberOfSuits );
newDeck = new String [ SizeOfDeck ];
int counter = 0;
for (int whatSuit = 1; whatSuit <= NumberOfSuits; whatSuit++) {
for (int rank = 1; rank <= NumberOfRanks; rank++) {
newDeck[counter++] = newCard.createCard(rank, whatSuit);
}
}
}
public void shuffleDeckofCards() {
int index;
int length = newDeck.length;
String temp;
Random random = new Random();
for ( int i = length - 1; i > 0; i-- ) {
index = random.nextInt(i+1);
temp = newDeck[index];
newDeck[index] = newDeck[i];
newDeck[i] = temp;
}
}
public String[] dealCards( int howManyCards ) {
this.howManyCards = howManyCards;
dealtDeck = new String[ howManyCards ];
System.arraycopy(newDeck, cardsDealtTotal, dealtDeck, 0, howManyCards);
cardsDealtTotal = cardsDealtTotal + howManyCards;
return dealtDeck;
}
@Override
public String toString() {
return ( "Deck of " + SizeOfDeck + "cards: low = 1 high = " +
SizeOfDeck + "top = Card " + newDeck [ cardsDealtTotal ] );
}
public int[] getHistogram( int numberOfCardsDealt ) {
int sum = 0; //initialize sum as 0
int count = 0; //initialize count 0
this.numberOfCards = numberOfCardsDealt - 1; //Equivalent array position to cards dealt
DeckofCards histoDeck = new DeckofCards();
do {
CardsDealtInTotal = CardsDealtInTotal + numberOfCards;
if ( SizeOfDeck < CardsDealtInTotal ) {
shuffleDeckofCards();
CardsDealtInTotal = 0;
}
for ( int i = 0; i <= numberOfCards; i++ ) {
sum = sum + histoDeck.getSumOfHand( dealtDeck[i]); //Check and send each position of hand to be added
histoSum[sum] +=1; //Based on sum add 1 to that position in the array
}
count+= 1;
} while ( count != 2 );
return histoSum;
}
public int getSumOfHand( String a) {
int value = 0;
String s;
s = a;
Pattern pattern = Pattern.compile("^S([\\d]+)R([\\d]+)$");
Matcher matcher = pattern.matcher(s);
if(matcher.find()){
value = (Integer.parseInt(matcher.group(1))*Integer.parseInt(matcher.group(2)));
}
return value;
}
}
Page 3.
public class Cards {
private int numberOfRanks;
private int numberOfSuits;
private int createCard;
private String theNumber;
private int whatSuit;
private String theSuit;
private String theCard;
public void setCards( int numberOfRanks, int numberOfSuits ) {
this.numberOfRanks = numberOfRanks;
this.numberOfSuits = numberOfSuits;
}
public String createCard( int newCard, int whatSuit ) {
createCard = newCard;
theNumber = Integer.toString( createCard );
theSuit = Integer.toString ( whatSuit );
theCard = ( "S" + theSuit + "R" + theNumber );
return theCard;
}
}
StackTrace?
Exception in thread "main" java.lang.NullPointerException
at MainClass.DeckofCards.getHistogram(DeckofCards.java:105)
at MainClass.MainClass.main(Assignment4.java:72)
C:\Users\mikel\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
This is my alternative option of the getHistogram() after making changes to case3 and the entire other method call. Using this I run into an issue with ArrayIndexOutOfBoundsException.
case 3:
numberOfCards = getCardDecision();
newDeck.getHistogram( numberOfCards );
//for ( String printHistogram : histogram ) {
// System.out.println ( printHistogram );
//}
break;
public void getHistogram( int numberOfCardsDealt ) {
int sum = 0;
int count = 0;
this.numberOfCardsDealt = numberOfCardsDealt;
this.numberOfCards = numberOfCardsDealt - 1;
CardsDealtInTotal = numberOfCardsDealt + numberOfCards;
DeckofCards histoDeck = new DeckofCards();
do {
if ( SizeOfDeck > CardsDealtInTotal ) {
String[] histogramDeck = dealCards ( numberOfCardsDealt );
for ( int i = 0; i <= numberOfCards; i++ ) {
sum = sum + histoDeck.getSumOfHand( histogramDeck[i]);
System.out.println ( sum );
}
}
else {
shuffleDeckofCards();
CardsDealtInTotal = 0;
}
count+= 1;
} while ( count != 6 );
}
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException
at java.lang.System.arraycopy(Native Method)
at MainClass.DeckofCards.dealCards(DeckofCards.java:74)
at MainClass.DeckofCards.getHistogram(DeckofCards.java:101)
at MainClass.MainClass.main(MainClass.java:72)
C:\Users\mikel\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
These errors occur at
newDeck.getHistogram ( numberOfCards );
System.arraycopy ( newDeck, cardsDealtTotal, dealtDeck, 0, howManyCards);
String[] histogramDeck = dealCards ( numberOfCardsDealt );
