Java求1-100的和

for循环

		int sum=0;
		for (int i = 100; i>=1; i--) {
			sum+=i;
		}
		System.out.println(sum);

while循环

		int sum=0;
		int i = 1;
		while(i<=100) {
			sum+=i;
			i++;
		}

do while循环

		int sum=0;
		int i=1;
		do {
			sum+=i;
			i++;
		}while(i<=100);