Here is the Deck.java file, I know for sure the error is here.
import java.util.List;
import java.util.ArrayList;
/**
* The Deck class represents a shuffled deck of cards.
* It provides several operations including
* initialize, shuffle, deal, and check if empty.
*/
public class Deck {
/**
* cards contains all the cards in the deck.
*/
private List<Card> cards;
/**
* size is the number of not-yet-dealt cards.
* Cards are dealt from the top (highest index) down.
* The next card to be dealt is at size - 1.
*/
private int size;
/**
* Creates a new <code>Deck</code> instance.<BR>
* It pairs each element of ranks with each element of suits,
* and produces one of the corresponding card.
* @param ranks is an array containing all of the card ranks.
* @param suits is an array containing all of the card suits.
* @param values is an array containing all of the card point values.
*/
public Deck(String[] ranks, String[] suits, int[] values) {
cards = new ArrayList<Card>();
for (int j = 1; j < ranks.length; j++) {
for (String suitString : suits) {
cards.add(new Card(ranks[j], suitString, values[j]));
}
}
shuffle();
}
/**
* Determines if this deck is empty (no undealt cards).
* @return true if this deck is empty, false otherwise.
*/
public boolean isEmpty() {
return size < 0;
}
/**
* Accesses the number of undealt cards in this deck.
* @return the number of undealt cards in this deck.
*/
public int size() {
return size;
}
/**
* Randomly permute the given collection of cards
* and reset the size to represent the entire deck.
*/
public void shuffle() {
for (int k = cards.size() - 1; k >= 0; k--) {
int howMany = k + 1;
int start = 0;
int randPos = (int) (Math.random() * howMany) + start;
Card temp = cards.get(k);
cards.set(k, cards.get(randPos));
cards.set(randPos, temp);
}
size = cards.size();
}
/**
* Deals a card from this deck.
* @return the card just dealt, or null if all the cards have been
* previously dealt.
*/
public Card deal() {
size--;
if (isEmpty()) {
return null;
}
Card c = cards.get(size);
return c;
}
/**
* Generates and returns a string representation of this deck.
* @return a string representation of this deck.
*/
@Override
public String toString() {
String rtn = "size = " + size + "\nUndealt cards: \n";
for (int k = size - 1; k >= 0; k--) {
rtn = rtn + cards.get(k);
if (k != 0) {
rtn = rtn + ", ";
}
if ((size - k) % 2 == 0) {
// Insert carriage returns so entire deck is visible on console.
rtn = rtn + "\n";
}
}
rtn = rtn + "\nDealt cards: \n";
for (int k = cards.size() - 1; k >= size; k--) {
rtn = rtn + cards.get(k);
if (k != size) {
rtn = rtn + ", ";
}
if ((k - cards.size()) % 2 == 0) {
// Insert carriage returns so entire deck is visible on console.
rtn = rtn + "\n";
}
}
rtn = rtn + "\n";
return rtn;
}
}
Here is the runner code. This is where I get the error: "Exception in thread "main" java.lang.NullPointerException at DeckTester.testShuffle(DeckTester.java:137) at DeckTester.main(DeckTester.java:15)" Ill comment the line number next to the lines affected.
* This is a class that tests the Deck class using assert statements.
*/
public class DeckTester {
/**
* The main method in this class checks the Deck operations for consistency
* using assert statements.
* @param args is not used.
*/
public static void main(String[] args) {
test2CardDeck();
test1CardDeck();
testShuffle(); //Line 15
System.out.println("All tests passed!");
}
/**
* Create a 1-card Deck and test the Deck methods with it.
*/
private static void test1CardDeck() {
String[] r1 = {"ace"};
String[] s1 = {"spades"};
int[] v1 = {1};
Deck d = new Deck(r1, s1, v1);
testOneCard(d, new Card("ace", "spades", 1));
testEmpty(d);
d.shuffle();
testOneCard(d, new Card("ace", "spades", 1));
testEmpty(d);
}
/**
* Create a 2-card Deck and test the Deck methods with it.
*/
private static void test2CardDeck() {
String[] r2 = {"ace", "2"};
String[] s2 = {"hearts"};
int[] v2 = {1, 2};
Deck d = new Deck(r2, s2, v2);
assert d.size() == 2 : "Initial size is " + d.size()
+ ". It should be 2.";
assert !d.isEmpty() : "Initial deck is empty.";
boolean aceIsFirst, twoIsFirst;
Card c = d.deal();
assert c != null : "1st card dealt is null.";
aceIsFirst = c.matches(new Card("ace", "hearts", 1));
twoIsFirst = c.matches(new Card("2", "hearts", 2));
assert (aceIsFirst || twoIsFirst) : "1st card dealt is " + c
+ ". It is not the one of the two correct cards.";
assert d.size() == 1 : "Size after one deal is " + d.size()
+ ". It should be 1.";
assert !d.isEmpty() : "Deck is empty after one deal.";
c = d.deal();
assert c != null : "2nd card dealt is null.";
if (aceIsFirst) {
assert c.matches(new Card("2", "hearts", 2)) : "2nd card dealt is "
+ c + ". It is not one of the two correct cards.";
} else {
assert c.matches(new Card("ace", "hearts", 1)) : "2nd card dealt is "
+ c + ". It is not one of the two correct cards.";
}
testEmpty(d);
d.shuffle();
c = d.deal();
assert c != null : "1st card dealt after shuffle is null.";
aceIsFirst = c.matches(new Card("ace", "hearts", 1));
twoIsFirst = c.matches(new Card("2", "hearts", 2));
assert (aceIsFirst || twoIsFirst) : "1st card dealt after shuffle is "
+ c + ". It is not the one of the two correct cards.";
assert d.size() == 1 : "Size is " + d.size()
+ "after shuffle and one deal. It should be 1.";
assert !d.isEmpty() : "Deck is empty after shuffle and one deal.";
c = d.deal();
assert c != null : "2nd card dealt after shuffle is null.";
if (aceIsFirst) {
assert c.matches(new Card("2", "hearts", 2))
: "2nd card dealt after shuffle is " + c
+ ". It is not the one of the two correct cards.";
} else {
assert c.matches(new Card("ace", "hearts", 1))
: "2nd card dealt after shuffle is " + c
+ ". It is not the one of the two correct cards.";
}
testEmpty(d);
}
/**
* Check that the given deck is empty.
* @param d is a deck that should be empty.
*/
private static void testEmpty(Deck d) {
assert d.size() == 0 : "Size for an empty deck is " + d.size()
+ ". It should be 0.";
assert d.isEmpty() : "isEmpty is false for an empty deck.";
Card c = d.deal();
assert c == null : "Dealt card is " + c
+ ". It should be null for an empty deck.";
}
/**
* Check that the given deck contains the given card and nothing else.
* @param d is a deck that should contain a single card.
* @param intended is the card that the one-card deck should contain.
*/
private static void testOneCard(Deck d, Card intended) {
assert d.size() == 1 : "Size is " + d.size()
+ ". It should be 1 for a 1-card deck.";
assert !d.isEmpty() : "isEmpty true for a 1-card deck.";
Card c = d.deal();
assert c != null : "1st dealt card is null for a 1-card deck.";
assert c.matches(intended) : "1st card dealt for a 1-card deck is "
+ c + ". It should be " + intended + ".";
}
/**
* Check that two decks constructed in succession aren't the same.
*/
private static void testShuffle() {
String[] r = {"ace", "2", "3", "4", "5", "6", "7", "8", "9", "10", "jack", "queen", "king"};
String[] s = {"spades", "hearts", "diamonds", "clubs"};
int[] v = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13};
Deck d1 = new Deck(r, s, v);
Deck d2 = new Deck(r, s, v);
assert d1 != d2 : "Decks d1 and d2 are the same physical object.";
assert d1.size() == d2.size() : "Deck d1 size of " + d1.size()
+ " does not match deck d2 size of " + d2.size() + ".";
boolean allMatch = true;
while (!d1.isEmpty()) {
Card c1 = d1.deal();
Card c2 = d2.deal();
if (c1.matches(c2)) { //Line 137
allMatch = false;
}
}
assert !allMatch : "The sequence of cards in d1 and d2 are identical.";
}
}```
