Question

1）提示用户输入两个正整数，并运算出两个数的加减乘除的结果输出出来 2）利用循环求N!。

Java程序

Answer 1

（1）
import java.util.Scanner;
public class Hello {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.println("请输入两个正整数：");
double a = scan.nextDouble();
double b = scan.nextDouble();
System.out.println("a+b=" + (a + b));
System.out.println("a-b=" + (a - b));
System.out.println("a*b=" + (a * b));
System.out.println("a/b=" + (a / b));
}
}
=====================================
测试结果：
请输入两个正整数：
6
3
a+b=9.0
a-b=3.0
a*b=18.0
a/b=2.0
（2）
import java.util.Scanner;

public class Hello {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.println("请输入正整数N");
int N = scan.nextInt();
int sum = 1;
for (int i = 1; i <= N; i++) {
sum = sum * i;
}
System.out.println("N! = " + sum);
}
}
=========================================
测试结果：
请输入正整数N
5
N! = 120

Answer 2

1、
public int add(int a,int b){
return a+b;
}
public int sub(int a,int b){
return a-b;
}
public int mul(int a,int b){
return a*b;
}
public double div(int a,int b){
return a/b;
}
2、
public int fac(int n){
int sum = 1;
while(n!=0){
sum = sum*n;
}
return sum;
}