问题:将一个数字反转,如：12345，进行反转为54321,；-12345，反转为-54321;

package ReverseInteger;

import org.junit.Test;
/*
 * 将一个数字反转,要判断数是大于0还是小于0
 * 然后对数字进行反转，利用while循环
 */
public class TestReverseInteger {
	@Test
	public void fun3() {
		int a = -12345;
		int b = reverseInteger1(a);
		System.out.println(b);
	}

	public int reverseInteger(int a){//数字反转的算法	 
		int sum = 0;
		while (a != 0) {
			sum = sum * 10 + a % 10;
			a = a / 10;
		}
		return sum;
	}

	//这个是分部计算的思路
	public int reverseInteger1(int a) {
		int sum = 0;
		if (a > 0){
			while (a > 0){
				sum = sum * 10 + a % 10;
				a = a / 10;
			}
			return sum;
		} 
		else if (a < 0) {
		  int b = -a;
		  while (b > 0){
				sum = sum * 10 + b%10;
				b = b / 10;
		  }
			return -sum;
		} 
		else {
			return sum;
		}
	}
}