所以我正在编写一个在控制台中播放的EvilHangman.java游戏。我相信你们之前都听说过这种类型的实验室，但它基本上可以尝试所有尝试而不是让用户获胜。每当我输入猜测时，我都会收到空指针错误。它与arraylists有关，以方法wordsLeft（）为中心。任何和所有的帮助都会很棒。我感到愚蠢，我无法弄明白，因为我在这个问题上花了最近几天。我对任务的处理方法可能不是解决问题的最有效方法，但这是我的实验室任务所需要的。有一个单词类可以上传字典中的所有英文单词。
while循环在我的主课程中完成游戏的所有工作：
while((numGuess != 0) ) {
if(remaining == true )
System.out.println("There are " + wordsLeft() + " possible words left.") ;
System.out.println("You have guessed these letters [" + allLetters + "]. And this is what your word looks like: " + patternHandler() ) ;
System.out.println("You have " + numGuess + " guess(es) left. Please enter a single letter guess: ") ;
String temp = keyboard.nextLine() ;
String guess = temp.toLowerCase() ;
if(guess.length() > 1) {
System.out.println("You entered too many characters. Enter a new guess. This did not use one of your guesses.") ;
temp = keyboard.nextLine() ;
guess = temp.toLowerCase() ;
}
if (alreadyGuessed(guess)){
System.out.println("You have already guessed that letter, please guess again. This did not use one of your guesses.");
temp = keyboard.nextLine() ;
guess = temp.toLowerCase() ;
}
if(!alreadyGuessed(guess)) {
allLetters += guess ; //keep track of all the letters that have already been guessed.
numGuess--;
count++ ;
}
currentList = Family.biggestList ;
System.out.println(patternHandler());
}
if(solved(patternHandler()))
System.out.println("You have won the game! Please play again!") ;
else
System.out.println("Sorry you have lost.. please try again!") ;
}//main
/**
* Checks to see if a letter has already been guessed.
* @param let the user's guess
* @return True if the letter has been guessed before
*/
private static boolean alreadyGuessed(String let) {
if(allLetters.length() == 0)
return false ;
for(int i = 0; i<=allLetters.length()-1 ; i++) {
if (allLetters.charAt(i) == let.charAt(0))
return true;
}
return false;
}//containsLetter
/**
* Decides whether or not the user wants to see how many words are possibly left
* @param temp user input, either yes or no.
* @return true if the user inputs yes.
*/
private static boolean runningTotal(String temp) {
if (temp.equalsIgnoreCase("yes"))
return true;
else
return false;
}//runningTotal
/**
* Checks to see if the user figured out the word.
* @param wrd the current pattern of the possible words
* @return true if the word does not contain '-'
*/
private static boolean solved(String wrd){
for(int i = 0; i<wrd.length(); i++){
if(wrd.charAt(i) == '-')
return false ;
}
return true ;
}//solved
/**
* Method to get the current word pattern.
* @return a string representation of the current word pattern.
*/
private static String patternHandler() {
String temp = "";
for(int i = 0; i<length; i++){
temp+= "-";
}
if(count == 0)
return temp ;
else
return Family.maxKey ;
}
/**
* Allows the user to know how many possible words are left.
* @param list the current word list of possible end words
* @return the size of list
*/
private static int wordsLeft() {
if(count==0)
return startList.size() ;
else
return Family.biggestList.size() ;
}
这部分在我的hashmap类中，它处理我想要使用的arraylist：
public static void main(String[] args) {
int guessesLeft = numGuess ;
int guessCount = numGuess ;
initial = Words.sortedWords[length] ;
if(guessesLeft == guessCount) {
getPatternForGuess(guess, initial) ;
guessCount-- ;
}
else
getPatternForGuess(guess, biggestList) ;
//the key of the wanted list
int maxLength = 0;
//longest list of patterns
biggestList = new ArrayList<String>() ;
for(ArrayList<String> entry : families.values()) {
if(biggestList == null || entry.size() > biggestList.size())
biggestList = entry ;
}
for(Entry<String, ArrayList<String>> e : families.entrySet()) {
int len = e.getValue().size() ; //size of the arraylist being looked at
if(maxKey == null || len > maxLength) {
maxKey = e.getKey() ;
maxLength = len ;
}
}
}//main
/**
* This method returns a HashMap of possible patterns and the words they contain.
* @param guess the user's guess obtained from EvilHangman
* @param list the list of possible words
* @return newMap a hashmap of all patterns and the ArrayList of words.
*/
public static HashMap<String, ArrayList<String>> getPatternForGuess(String guess, ArrayList<String> list) {
HashMap<String, ArrayList<String>> newMap = new HashMap<String, ArrayList<String>>() ;
String pattern = "" ;
for(int i = 0; i<list.size(); i++) {
String word = list.get(i) ;
pattern = getPatternForWord(guess, word) ;
if(!newMap.containsKey(pattern)) {
ArrayList<String> wordList = new ArrayList<String>() ;
wordList.add(word) ;
newMap.put(pattern, wordList) ;
}
if(newMap.containsKey(pattern)) {
ArrayList<String> wordList = new ArrayList<String>() ;
wordList.add(word) ;
}
}
return newMap ;
}//getPatternForGuess
//This method gets the pattern based on your guess and words like
/**
* Gets the pattern of the word based on the user guess
* @param guess the user guess obtained from evil hangman
* @param word the word pulled from the arraylist being mapped
* @return word a string representation of the pattern.
*/
public static String getPatternForWord(String guess, String word) {
char ch = guess.charAt(0) ;
for(int i = 0; i<word.length(); i++) {
if(word.charAt(i) != ch)
word.replace(word.charAt(i), '-') ;
}
return word;
}//getPatternForWord