Java之累加和

package com.cdp.leijiahe;

import java.util.Scanner;

public class leijiahe {

	/**
	 * 一个字节 = 8位二进制00000000
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		// 累加和
		long sum = 0;
		long a = 1;
		int n = 0;
		// 从键盘输入n
		System.out.println("请输入n的值：");
		Scanner input = new Scanner(System.in);
		n = input.nextInt();
		for (int i = 0; i < +n; i++) {
			sum = sum + a;
			// 每一项的变化
			a = a * 2;
		}
		System.out.println("累加和为：" + sum);
	}

}