Question

用java编写一个程序，计算1！+2！+3！+4！+5！

Answer 1

public class Demo {
public static void main(String[] args) {
int num = 5;
int sum = 0;
for (int i = num; i >= 1; i--) {
int tempSum = 1;
for (int j = 1; j <= i; j++) {
tempSum *= j;
}
sum += tempSum;
}
System.out.println("最后答案为：" + sum);
}
}
/* 运行结果:
* 最后答案为：153
*/

Answer 2

public class Test {

public static void main(String[] args) {
System.out.println(method(5));
}
//mehtod()方法进行递归调用
public static int method(int n) {
if (n == 1){
return 1;
}else{
return n*method(n-1);
}
}
}

Answer 3

public class Change {

public static void main(String[] args) {
System.out.println(jiecheng(5));
}

public static long jiecheng(int x){
if(x==1){
return 1;
}else{
return x*jiecheng(x-1);
}

}

Answer 4

int s = 0;
int m = 1;
for(int i = 1; i <= 5; i++)
{
m *= i;
s += m;
}

Answer 5

public class Test{
public static void main(String[] args) {
System.out.println(js(5));
}
public static int js(int n){
int sum=0;
for(int i=1;i<=n;i++){
sum+=jc(i);
}
return sum;
}

//求阶乘的方法
public static int jc(int n){
int sum=1;
for(int i=1;i<=n;i++){
sum*=i;
}
return sum;
}
}