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我用Java创建了一个Palindrome程序，它接受用户输入的一个或多个单词并将它们放入一个数组中。然后它接受反向输入并将其放入另一个数组中。然后我检查两个单词是否相同。

我的问题是程序正在改变其中一个字母，这样它总是正确的并且迭代次数太多了。关于我的代码中是什么导致这个的任何想法？

public static boolean isPalindrome(char[] a, int used){
char[] original = a;
int newNumber = used - 1;
for(int i = 0; i <= newNumber; i++){
  a[i] = a[newNumber - i ];
  System.out.println("Your original word was: " + String.valueOf(original));
  System.out.println("Backwards, your word is: " + String.valueOf(a));

  }
if(String.valueOf(original).equalsIgnoreCase(String.valueOf(a))){
  System.out.println("Your word or words are palindromes.");

}else{
  System.out.println("Your word or words are not palindromes");
}
return(String.valueOf(original).equalsIgnoreCase(String.valueOf(a)));
}

public void userInput(){
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter a word or words that you believe are palindromes: ");
word = keyboard.next();
word = word.replaceAll("\\W","");
int length = word.length();
char[] p = new char[length];
for(int i = 0; i < length; i++){
  p[i] = word.charAt(i);
}
Palindrome.isPalindrome(p, length);

}

当我输入“Candy”时，这是我的输出。

Your original word was: yandy
Backwards, your word is: yandy
Your original word was: ydndy
Backwards, your word is: ydndy
Your original word was: ydndy
Backwards, your word is: ydndy
Your original word was: ydndy
Backwards, your word is: ydndy
Your original word was: ydndy
Backwards, your word is: ydndy
Your word or words are palindromes

感谢大家的回答！这是正确的代码，尽管效率不高：

  public static boolean isPalindrome(char[] a, int used){
    char[] original = a;
    char[] newArray = new char[used];
    int newNumber = used - 1;
    for(int i = 0; i <= newNumber; i++){
      newArray[i] = a[newNumber - i ];
      }
     System.out.println("Your original word was: " + String.valueOf(original));
     System.out.println("Backwards, your word is: " + String.valueOf(newArray));

    if(String.valueOf(original).equalsIgnoreCase(String.valueOf(newArray))){
      System.out.println("Your word or words are palindromes.");

    }else{
      System.out.println("Your word or words are not palindromes");
    }
    return(String.valueOf(original).equalsIgnoreCase(String.valueOf(newArray)));
    }

Answer 1

在你的回文功能中： -

for(int i = 0; i <= newNumber; i++){
          a[i] = a[newNumber - i ];
          System.out.println("Your original word was: " + String.valueOf(original));
          System.out.println("Backwards, your word is: " + String.valueOf(a));

          }

这里你要替换现有的数组。

您甚至可以尝试以下代码： -

String original, reverse="";
              Scanner in = new Scanner(System.in);

              System.out.println("Enter a string to check if it is a palindrome");
              original = in.nextLine();

              int length = original.length();

              for ( int i = length - 1 ; i >= 0 ; i-- )
                 reverse = reverse + original.charAt(i);

              if (original.equals(reverse))
                 System.out.println("Entered string is a palindrome.");
              else
                 System.out.println("Entered string is not a palindrome.");

Answer 2

如果您想以这种简单的方式查看palindrome，可以尝试使用StringBuilder。

public static boolean isPalindrome(String input) {
    StringBuilder sb=new StringBuilder(input);
    return input.equals(sb.reverse().toString());
}

根据您的情况更改isPalindrome方法，如下所示

 public static void isPalindrome(char[] a, int used){
    char[] newArr = new char[a.length]; // create a new array in same length as a
    int newNumber = used - 1;
    System.out.println("Your original word was: " + String.valueOf(a));
    for(int i = 0; i <= newNumber; i++){
        newArr[i] = a[newNumber - i ];
    }
    System.out.println("Backwards, your word is: " + String.valueOf(newArr));
    if(String.valueOf(newArr).equalsIgnoreCase(String.valueOf(a))){
        System.out.println("Your word or words are palindromes.");
    }else{
        System.out.println("Your word or words are not palindromes");
    }
}

Answer 3

问题在于您的代码a[i] = a[newNumber - i ];正在更改现有数组。

首先创建一个新数组，然后将反向字符串放入其中。

    public static boolean isPalindrome(char[] a, int used) {
    char[] newA = new char[a.length];
    int newNumber = used - 1;
    for (int i = 0; i <= newNumber; i++) {
        newA[i] = a[newNumber - i];
        System.out.println("Your original word was: " + String.valueOf(a));
        System.out.println("Backwards, your word is: " + String.valueOf(newA));
    }
    if (String.valueOf(String.valueOf(newA)).equalsIgnoreCase(String.valueOf(a))) {
        System.out.println("Your word or words are palindromes.");

    } else {
        System.out.println("Your word or words are not palindromes");
    }
    return (String.valueOf(String.valueOf(newA)).equalsIgnoreCase(String.valueOf(a)));
}

还有许多其他有效的方法来编写此代码。

Answer 4

无需复制数组（您只复制了参考文献），只创建了一个大小相同的新数组，并使用a作为原始数组。
```
char[] reverse = new char[used];
```

将system.out放在for循环之外：

for(int i = 0; i <= newNumber; i++){
    reverse[i] = a[newNumber - i ];
}
System.out.println("Your original word was: " + String.valueOf(a));
System.out.println("Backwards, your word is: " + String.valueOf(reverse));

整个是thePalindrom功能：

public static boolean isPalindrome(char[] a, int used){
    char[] reverse = new char[used];
    int newNumber = used -1;
    for(int i = 0; i <= newNumber; i++){
        reverse[i] = a[newNumber - i ];
    }
    System.out.println("Your original word was: " + String.valueOf(a));
    System.out.println("Backwards, your word is: " + String.valueOf(reverse));

    if(String.valueOf(reverse).equalsIgnoreCase(String.valueOf(a))){
      System.out.println("Your word or words are palindromes.");

    }else{
      System.out.println("Your word or words are not palindromes");
    }
    return(String.valueOf(reverse).equalsIgnoreCase(String.valueOf(a)));
}

Answer 5

问题出在您分配的isPalindrome方法

char[] original = a;

char []变量是引用。通过设置original = a，您将复制引用，因此现在两个数组都指向同一块内存。

现在，当您修改a时，original也会被修改，因为它们都指向同一个内存。

您可以通过创建新实例来解决此问题，如下所示：

    char[] original = new char [a.length];
    System.arraycopy( a, 0, original, 0, a.length );

Palindrome程序没有在Java中提供正确的输出

5 个答案: