java学习p153

public class a1 {
    public static void main(String[] args) {
        int sum1 = 0;
        int total1 = 0;
        for (int i = 1;i <= 100;i++) {
            sum1 += i;
            total1 += sum1;
        }
        System.out.println("方法1结果为 " + total1);
        ///
        int sum2 = 0;
        int total2;
        for (int i = 1;i <= 100;i++)
            sum2 += i;
        total2 = sum2;
        for (int i = 100;i >= 2;i--) {
            sum2 = sum2 - i;
            total2 += sum2;
        }
        System.out.println("方法2结果为 " + total2);
        ///
        int total3 = 0;
        for (int i = 1;i <= 100;i++)
            for (int j = 1;j <= i;j++)
                total3 += j;
        System.out.println("方法3结果为 " + total3);
    }
}