实现递归的简单实例

求：1*1+2*2+3*3+...=?
public class RecursiveTest {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(countDown(10));
}
/**
* 1*1+2*2+3*3+...=?
* @param n
* @return
*/
public static int countDown(int n) {
int sum ;

if (n==1) {
sum=1;
} else {
sum = countDown(n-1)+n*n;
}
return sum;
}
}

如果求(1*1-1)+(2*2-1)+(3*3-1)+...=?
public static int countDown(int n) {
int sum ;
if (n==1) {
sum=1;
} else {
sum = countDown(n-1)+n*n-1;
}
return sum;
}