Java将单个字符与字符数组进行比较

Question

I need to compare single char to char array and see if array has that char.

My current code looks like this:

public boolean isThereChar(char[] chaArray, String chr){
    boolean bool = false;
    for(int i=0; i < chaArray.length; i++)
            {
                if(chr.equals(chaArray[i])){
                    bool = true;
                }
            }
            return bool;
}

Edit Notes:

Really sorry for being confusing! I am just a Java Beginner =/
Basically I am writing small Hangman game with GUI.
My program reads off text file and randomly chooses word which player has to guess, then prints it out in hidden manner like this: _ _ _ _ _
In this case I want player to input character or string (person can guess either whole word or just one letter)
Then I want my program to take that letter or string and compare to my hidden word

Following code chooses word and hides it:

public String pickWord(){
    String guessWord = (wordsList[new Random().nextInt(wordsList.length)]);
    return guessWord.toLowerCase();
}

//Hides picked word
public char[] setWord(){
    char[] word = new char[pickWord().length() * 2];
    for (int i = 0; i < word.length; i+=2) {
        word[i] = '_';
        word[i + 1] = ' ';
    }
    return word;
}

Then person input his character which he guesses to program with following code:

public void actionPerformed(ActionEvent e) {
    String action = e.getActionCommand();

    if (action == "Guess Letter"){
        inputChar = JOptionPane.showInputDialog("Please enter letter (a-z)");
        if (inputChar.length() > 1){
            GuessedLetters glr = new GuessedLetters(inputChar);
            glr.setInString(inputChar);
            //For testing purposes
            System.out.println("This is String: " +glr.getInString());              
        }else{
        GuessedLetters glr = new GuessedLetters(inputChar);
        glr.setInChar(inputChar);
        //For testing purposes
        System.out.println("This is Char: " +glr.getInChar());
        }
    }

Lastly I want to take that character which was inputted and compare to my array of chars which is my hidden word:

public boolean isThereChar(char[] array, String str){
    return isThereChar(array, str.charAt(0));
}

public boolean isThereChar(char[] array, char c){
    for(int i=0; i<array.length; i++){
        if (array[i] == c) return true;
    }
    return false;
}

I want to check what does my code returns (true or false), but I keep failing at doing so. (Right now I am trying to call method in my main class to check it, if you can give me tips how to do it otherwise please let me know.)

Answer 1

I would use: Chars.contains(array, chr); with Guava Chars

Answer 2

The NullPointerException is happening because either chaArray or chr is null when you call the method. ( And if not, then the NullPointerException is occurring somewhere else!! )

The other problem with your code is this line:

  if (chr.equals(chaArray[i])) {

Since chr is actually a String, what is going to happen here is that the value of chaArray[i] will be auto-boxed as a Character object, and then passed as an argument to String.equals(Object) . But the String.equals(Object) will return false unless its argument is a String ... so your code wouldn't find the character anyway.

You need to either compare the character like this:

  if (chr.charAt(0) == chaArray[i]) {

or declare chr to be a char and compare it as:

  if (chr == chaArray[i]) {

Answer 3

Let's see if I got what you need :

public void actionPerformed(ActionEvent e) {
    String action = e.getActionCommand();
    if (action == "Guess Letter"){
        inputChar = JOptionPane.showInputDialog("Please enter letter (a-z)");
        if (inputChar.length() > 1){ //User input is a string here, right?
            GuessedLetters glr = new GuessedLetters(inputChar);
            glr.setInString(inputChar);
            System.out.println(wordToGuess.contains(glr.getInString())); //This will print true if wordToGuess is equal to glr.getInString() or if it just contains it
            //For testing purposes
            System.out.println("This is String: " +glr.getInString());              
        }else{ //Here the user gave us just a character, so we've got to know if this character is contained in the word, right?
        GuessedLetters glr = new GuessedLetters(inputChar);
        glr.setInChar(inputChar);
        System.out.println(wordToGuess.contains(glr.getInChar()); //This will print true if your char is in the wordToGuess string
        //For testing purposes
        System.out.println("This is Char: " +glr.getInChar());
        }
    }
}

Answer 4

String chr might be null causing NullPointerException .

Use char chr instead of String .

public boolean isThereChar(char[] chaArray, char chr){
    boolean bool = false;
    for(int i=0; i < chaArray.length; i++) {
        if(chr==chaArray[i])){
             bool = true;
        }
    }
    return bool;
}

Answer 5

Select the character from the parameter passed in, or pass in a char eg

chr[0]

or

public String isThereChar(char[] chaArray, char chr){
    for(int i=0; i < chaArray.length; i++)
            {
                if(chr.equals(chaArray[i])){
                    return chr;
                }
            }
            return "Guess Again";
}

Answer 6

public boolean  isThereChar(char[] chaArray, char chr){        
for(int i=0; i < chaArray.length; i++)
        {
            if((chaArray[i]==chr)){
                return true;   // means Character exist in the Character array
            }
        }
        return false;  //// means Character does not exist in the Character array
}