Question

In this project you will create a basic console based calculator program.
The calculator can operate in two modes: Standard and Scientific modes. 
The Standard mode will allow the user to perform the following operations: 
(+, -, *, /) add, subtract, multiply, and divide
The Scientific mode will allow the user to perform the same functionality as the Standard 
add, subtract, multiply, and divide (+, -, *, / ) plus the following: 
sin x, cos x, tan x. (sin x, cos x, tan x)
The calculator should be able to perform addition, subtraction, multiplication, and division of two or more numbers but perform sin x, cos x, and tan x of one number only (the number is in radians). 

1. The calculator program will first ask the user for the mode to operate in (Standard or Scientific)

      Sample Output: 
      Enter the calculator mode: Standard/Scientific?
      Standard

2. The program should then ask the user for the operation to execute (+, -, *, /, sin x, cos x, tan x)

      Sample Output for Scientific mode:
      Enter '+' for addition, '-' for subtractions, '*' for multiplication, '/' for division, 'sin' for sin x, 'cos' for cos x, 'tan' for tan x:
      sin

      Sample Output for Scientific mode:
      Enter '+' for addition, '-' for subtractions, '*' for multiplication, '/' for division, 'sin' for sin x, 'cos' for cos x, 'tan' for tan x:
      sin

2a. If the user enters an invalid operation, output a message telling the user the input is invalid and re-prompt the user for the operation again.

      Enter '+' for addition, '-' for subtractions, '*' for multiplication, '/' for division, 'sin' for sin x, 'cos' for cos x, 'tan' for tan x:
      division 

      Invalid operation entered

      Enter '+' for addition, '-' for subtractions, '*' for multiplication, '/' for division, 'sin' for sin x, 'cos' for cos x, 'tan' for tan x:
      / 

3. In order to know how many times the user will need to perform the operation, prompt the user for the number of double values they want to enter (All numbers in this program are double), then ask the user to enter the numbers. 

      Sample Output:
      How many numbers do you want to subtract:
      3
      Enter 3 numbers:
      4
      35
      9

In this example the calculator will calculate 4 + 35 + 9. The result will be 48.

The calculator should be able to perform the following operations:

      2+3 = 5
      3+6+1+1+1 = 12
      1-2-90 = -91
      10*2*3 = 60
      10/2/5 = 1
      cos(0) = 1
      sin(0) = 0
      tan(0) = 0

Note: This calculator does NOT support multiple operations in the expressions like: 10+2-8
Note: Multiple numbers are only acceptable for the operations of (+, -, *, / ) not for (sin,cos,tan)

4. Display the result
      Sample Output:
      Result: 50.0

5. Finally, output the result to the user and ask the user if he/she want to start over. 
      Sample Output:
      Start over? Y/N
      Y

Full Sample Output:
Enter the calculator mode: Standard/Scientific?
Standard

Enter '+' for addition, '-' for subtractions, '*' for multiplication, '/' for division, 'sin' for sin x, 'cos' for cos x, 'tan' for tan x:
addition

Invalid operation entered

Enter '+' for addition, '-' for subtractions, '*' for multiplication, '/' for division, 'sin' for sin x, 'cos' for cos x, 'tan' for tan x:
+

How many numbers do you want to subtract:
3
Enter 3 numbers:
4
35
9
Result: 48.0
Start over? Y/N
Y
Enter the calculator mode: Standard/Scientific?
Scientific

Enter '+' for addition, '-' for subtractions, '*' for multiplication, '/' for division, 'sin' for sin x, 'cos' for cos x, 'tan' for tan x:
sin

Enter number in radians to find sin:
1.5708
Result: 1
Start over? Y/N
N

Answer 1

/******************************************************************************

Online Java Compiler.
Code, Compile, Run and Debug java program online.
Write your code in this editor and press "Run" button to execute it.

*******************************************************************************/

public class Main
{
int modeCount;
public showStOperation(){
       System.out.println(" Enter '+' for addition, '-' for subtractions, '*' for multiplication, '/' for division");
  
}
public showScOperation(){
System.out.println("Enter '+' for addition, '-' for subtractions, '*' for multiplication, '/' for division, 'sin' for sin x, 'cos' for cos x, 'tan' for tan x:");
  
}
public void modeCount(int count){
this.modeCount=count;
}
public void addition(){
       Scanner myObj = new Scanner(System.in); // Create a Scanner object
int sum=0;
for(int i=0;i<count;i++){
sum=sum+myObj.nextInt();
}
        System.out.println("The sum is "+sum);

}
  
  
   public static void main(String[] args) {
   Main main=new Main();
       System.out.println("Enter the calculator mode: Standard/Scientific?");
       Scanner myObj = new Scanner(System.in); // Create a Scanner object
String mode = myObj.nextLine();
if(mode.equalIgnoreCase("standard")){
main.showStOperation();
}
else if(mode.equalIgnoreCase("scientific")){
main.showScOperation();
}
else{
        System.out.println("Invalid calculator");

}
   System.out.println("How many numbers do you want to perform");
int count = myObj.nextInt();
main.modeCount(count);
  
   }
}

Since the question has many part I am answering only 4