Question

我正在编写一个程序，查找最多8个字符的单词/短语是否是回文。无论我输入什么作为输入，即使它是回文，我的程序打印我的else语句。我检查并确保我写的代码实际上反向打印输入，它确实。所以我不太清楚问题是什么。

import java.util.Scanner;
public class hw5 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String word, newWord;
int lengthOfWord;
char lc;//last character

    System.out.print("Enter word/phrase of 8 characters or less: ");
    word = in.nextLine();

    word = word.toLowerCase();
    newWord = word;
    lengthOfWord = word.length();
    lc = word.charAt(lengthOfWord -1);


    lc = word.charAt(lengthOfWord -1);

    if (word.length() == 2)
        newWord = lc+word.substring(0,1);
    else if (word.length() == 3)
        newWord = lc+word.substring(1,2)+word.substring(0,1);
    else if (word.length() == 4)
        newWord = lc+word.substring(2,3)+word.substring(1,2)+word.substring(0,1);
    else if (word.length() == 5)
        newWord = lc+word.substring(3,4)+word.substring(2,3)+word.substring(1,2)+word.substring(0,1);
    else if (word.length() == 6)
        newWord = lc+word.substring(4,5)+word.substring(3,4)+word.substring(2,3)+word.substring(1,2)+word.substring(0,1);
    else if (word.length() == 7)
        newWord = lc+word.substring(5,6)+word.substring(4,5)+word.substring(3,4)+word.substring(2,3)+word.substring(1,2)+word.substring(0,1);
    else if (word.length() == 8)
        newWord = lc+word.substring(6,7)+word.substring(5,6)+word.substring(4,5)+word.substring(3,4)+word.substring(2,3)+word.substring(1,2)+word.substring(0,1);
    else
        newWord = "error, not enough or too many characters";

    if (newWord == word)
        System.out.println("it is a palindrome");
    else
        System.out.println("it is not a palindrome");

    System.out.println(newWord);

Answer 1

你可以让它变得更简单。

word = word.toLowerCase();
newWord = new StringBuilder(word).reverse().toString();

if (newWord.equals(word))
     System.out.println("it is a palindrome");
 else
      System.out.println("it is not a palindrome");

Answer 2

if (newWord.equals(word))
        System.out.println("it is a palindrome");
else
        System.out.println("it is not a palindrome");

使用==时，不比较单词，比较的是内存中两个变量的索引。

Answer 3

==表示运行时将检查它们是否指向同一地址，equals将检查这两个对象是否具有相同的内容。因此，请尝试使用equals方法比较字符串和==数字。

Answer 4

String是对象。字符串变量只是指向字符串对象的指针。因此，当你执行if(newWord==word)时，你不是要比较字符串的内容，而是比较这些指针中的值（指针指向的内存位置）。您需要使用String的{{1}}方法来比较两个字符串的内容。

为什么我的if语句不能正常工作？

4 个答案: