Java关于Palindrome Number 的题目解答，palindromenumber

Java关于Palindrome Number 的题目解答，palindromenumber

题目

Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.
确定整数是不是回文数，当整数向前和向后读相同的时候，就是回文数
Example 1:

Input: 121
Output: true
Example 2:

Input: -121
Output: false
Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
说明：从左向右为-121，从右向左为121-，所以它不是回文数
Example 3:

Input: 10
Output: false
Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
说明:从右向左读为01，因此它不是回文数
Follow up:

Coud you solve it without converting the integer to a string
你能不能将整数换为字符串？

代码

class Solution {
 public boolean isPalindrome(int x) {
  if(x<0)
  {
return false;
  }
  if(x==0)
  {
return true;
  }
  StringBuilder in = new StringBuilder();
  int a = x;
  while(a!=0)
  {
in.append(a%10);
a/=10;
  }
  String o = String.valueOf(x);
  if(o.equals(in.toString()))
  {
return true;
  }else
  {
return false;
  }
 }
}

注意不要使用StringBuffer,StringBuffer在单线程下效率并不高。

StringBuffer为287ms

StringBuilder为99ms

可以看出StringBuffer在单线程下的重复加锁解锁操作耗费了大量时间