java - How to compare two StringBuffer Objects using .equals() method?

Question

The following code did not work. Can anyone tell me what's wrong with the following code. Logically it should work...

package assignments;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class IsPalindrome {
public static void main(String[] args) throws IOException {
    BufferedReader br = new BufferedReader(
                                      new InputStreamReader(System.in));
    System.out.println("Enter a Word:");
    StringBuffer sb1 = new StringBuffer(br.readLine());
    StringBuffer sb2 = new StringBuffer(sb1);
    sb1.reverse();

    if(sb2.equals(sb1))
        System.out.println("Palindrome");
    else
        System.out.println("Not a Palindrome");
}
}

Answer 1

尝试

sb1.toString().equals(sb2.toString());

因为StringBuffer#toString方法返回存储在缓冲区内的数据的 String 值：

返回表示此序列中数据的字符串。分配并初始化一个新的 String 对象以包含该对象当前表示的字符序列。然后返回此字符串。对该序列的后续更改不会影响字符串的内容。

Answer 2

在 StringBuffer 类equals中的方法不会像在String类中那样被覆盖。StringBuffer它只是查看引用是否相同。因此，您首先需要将其转换为字符串，然后使用 equals 方法。

所以试试

sb1.toString().equals(sb2.toString());

Answer 3

You can write

System.out.println("Enter a line:");
String line = br.readLine().replace(" ", ""); // palindromes can have spaces
String reverse = new StringBuilder(sb1).reverse().toString();

if(line.equals(reverse))
    System.out.print("Not a ");
System.out.println("Palindrome");