1)

import java.util.*;
public class Calculate {

       public static void main(String[] args) {
          Scanner input=new Scanner(System.in);
          double num1;    
          double num2;   
          char operator;      
          double result;       

          System.out.println("Enter expressions such as  17 + 3 or 3.14159 * 4.7");
          System.out.println("Use any of the operators +, -, *, /.");
          System.out.println("To end, enter a 0.");

          while (true){
              System.out.println();
              System.out.println("Enter Expression: ");
              num1 = input.nextDouble();
              if (num1 == 0)
                 break;
              operator = input.next().charAt(0);
              num2 = input.nextDouble();

              switch (operator) {
                  case '+':
                     result = num1 + num2;
                     break;
                  case '-':
                     result = num1 - num2;
                     break;
                  case '*':
                     result = num1 * num2;
                     break;
                  case '/':
                     result = num1 / num2;
                     break;
                  default:
                    System.out.println("Unknown operator: " + operator);
                     continue;  
              } 
          System.out.println("Result is " + result);
        }
      } 
    }

2)

import java.util.*;
class  Factorial{
    public static void main(String[] args) 
    {
        Scanner input=new Scanner(System.in);
        System.out.print("Enter value of m: ");
        int m=input.nextInt();
        long num=m;
        for(int i=m;i>1;i--){
            num=num*(i-1);
        }
        System.out.println(num);
    }
}