如何将char数组传递给方法并返回布尔值

Question

I am trying to write a program which checks whether a word is a palindrome or not. My code compiles butthe code in the isItPalindrome method doesn't seem to be run at all. I'm hoping someone can point out where i have gone wrong. Here is my code:

class Main
{
public static void main ( String args[] )
{
    System.out.print ("#Enter word");
    String word = BIO.getString();

    String wordLowerCase = word.toLowerCase();                                        // converts word to lower case (only way i could think of to ignore case)
    char letters[] = wordLowerCase.toCharArray();                                     // converts string into an array of character


    while ( !word.equals ("END")){
        if (isItPalindrome(letters) == true)
        {
            System.out.print (""+word+"");
            System.out.println ("   is a palindrome");

        }
        else if (isItPalindrome(letters) == false)
        {
            System.out.print (""+word+"");
            System.out.println ("   is not a palindrome");
        }

        System.out.print ("#Enter word");
        word = BIO.getString();

    }

}

public static boolean isItPalindrome ( char letters[]){

    boolean palindrome = true;
    if (letters.length%2 == 0){
        for (int index=0; index<letters.length/2-1; index++)                              //index will finish at letters/2  
        {
            if (letters[index] != letters[letters.length-index-1])                                       //checks if index is the same as its opposite letter
            {
                return false;

            }
            else                                                                         //if any pairs of letters are not in ascending order then it returns fasle and breaks out of the loop
            {
                palindrome = true;

            }

        }
    }
    else{
        for (int index = 0; index < (letters.length-1)/2-1; index++)
        {
            if (letters[index] != letters[letters.length-index-1]){

                return false;

            }
            else{

                palindrome = true;
            }  

        }
    }

    return palindrome;
}

}

Answer 1

Besides the initial word, your character array letters never reflects the current word in your while loop inside your main method. I don't know what you mean when you say your method "doesn't seem to be run at all" but I assume that you meant it's being run with the wrong output. This is one reason why. Be sure to call

wordLowerCase = word.toLowerCase();
letters = wordLowerCase.toCharArray();

every iteration of the while loop.

Side note: In your isItPalindrome method, you do not even need any of the else statements or the boolean palindrome at all. Simply return false if you ever find a case when the word is not a palindrome like you currently are. Then, if you have gotten to the end of the word, it must be a palindrome and you can return true .

Answer 2

There were some issues in the main-method, for example the char-array was never updated and the palindrome-method was far to complicated, here is the working version:

public static void main(String args[]) {
    System.out.print("#Enter word: ");
    String word = BIO.getString();

    while (!word.equals("END")) {
        char[] letters = word.toLowerCase().toCharArray();

        if (isItPalindrome(letters) == true) {
            System.out.println(word + "   is a palindrome");
        } else {
            System.out.print(word + "   is not a palindrome");
        } // OR
        // Use this one-liner instead of the if:
        // System.out.println(word + isItPalindrome(letters) ?
        //                     "   is a palindrome" : "   is not a palindrome");

    System.out.print("#Enter word: ");
    word = BIO.getString();
    }

}

public static boolean isItPalindrome(char letters[]) {
    for (int i = 0; i < letters.length / 2; i++) {
        if (letters[i] != letters[letters.length - i - 1]) {
            return false;
        }
    }

    return true;
}

Hope this helps.

Answer 3

First, to answer the question that's in the title:

public boolean palindrome(char C)

Has a return type of boolean but requires that you pass it a Character.

Second:

You're over-complicating things in the way that you reverse the words to check them. You could simply take the word, as a String, and take it apart, putting it into an array of Characters . Then put each char variable into a Stack . Then as you take them out of the stack, piece by piece, copy them to another array of Character s.