Java Palindrome checker

问题

I have a issue with my palindrome checker as it is not working properly. It must be able to test these 4 things:

    TestPalindrome("Madam, I'm Adam", true);
    TestPalindrome("addbda", false );
    TestPalindrome("", false);
    TestPalindrome("Dammit, I'm mad", true);

This is my code for the palindrome:

public static boolean IsPalindrome( String inputString )
{
    String reverse = "";
    for(int i = inputString.replaceAll("[^a-zA-Z ]", "").length() -1; i>=0; i--){
        reverse = reverse + inputString.replaceAll("[^a-zA-Z ]", "").charAt(i);
    }
    if(inputString.replaceAll("[^a-zA-Z ]", "").equalsIgnoreCase(reverse.toString()) && !inputString.replaceAll("[^a-zA-Z ]", "").isEmpty()){
        return true;
    }

    if(!inputString.replaceAll("[^a-zA-Z ]", "").equalsIgnoreCase(reverse.toString()) && !inputString.replaceAll("[^a-zA-Z ]", "").isEmpty()){
        return false;
    }

    if(inputString.replaceAll("[^a-zA-Z ]", "").isEmpty()){
        return false;
    }

    else return true;
         }
}

This is what my output is:

TestPalindrome failed: expected true got false
TestPalindrome passed!
TestPalindrome passed!
TestPalindrome failed: expected true got false

Can anyone help me fix this so I get all passes in the list. I understand similar questions have been asked but I´m not asking how to do a palindrome checker but how to fix my specific one. I used those other questions to learn but for some reason my one doesn't work.

回答1:

In order to such algorithm to work you need to consider to clean the punctual symbols like comma, semmicolon, aposthrofs etc (am talking about ';:' etc)

Java has a StringBuilder class and in there is a method to reverse strings

so if you clean the String to check, reverse it and compare it again itself you can see if it a palindrome or not...

Example:

public static void main(String[] args) {
    String word = "Madam, I'm Adam";
    String word2 = "addbda";
    String word3 = "";
    String word4 = "Dammit, I'm mad";
    System.out.println(IsPalindrome(word));
    System.out.println(IsPalindrome(word2));
    System.out.println(IsPalindrome(word3));
    System.out.println(IsPalindrome(word4));
}

private static boolean IsPalindrome(String word) {
    String wordClean = word.replaceAll("[^a-zA-Z  ]", "");
    String reversedWord =  new StringBuilder(wordClean).reverse().toString();
    System.out.println(wordClean);
    System.out.println(reversedWord);
        return reversedWord.equalsIgnoreCase(wordClean)&&!wordClean.isEmpty();
}

this will print

MadamImAdam madAmImadaM true

addbda adbdda false

false (empty check)

DammitImmad dammItimmaD true

回答2:

You are not removing spaces, so only strings with spaces in the same places are good. Just use [^a-zA-Z] against [^a-zA-Z ]

来源：https://stackoverflow.com/questions/36534673/java-palindrome-checker