Thread: I'm starting on java development. What is wrong on this calculator?

I'm trying to make a calculator as my first program java program and something is wrong. When the calculator asks me to do other operation and I choose "Yes" or "No", then it asks me 2 times before doing anything, ignoring the first input, any idea of why?
Also, it's a bit too much complicated for what it does but I don't know how to fix that mess. If you have some tips for simplifiying this, I would love to read them.

[SOLUTION]
Lines 27, 36, 45, 55 and 68 are calls to the Oper method and the following line to each of those (28, 37, 46, 56 and 69) are if statements with that call in the condition.
I just deleted those lines and leave only the if statement and now it works as I wanted
[/SOLUTION]

import java.util.Scanner;
public class Calculator{
	public static void main(String[] args){
		long n1, n2, res, rem;
		char op = 'a';
		boolean otOp = true;
		Scanner sc1 = new Scanner(System.in);
		while(otOp == true){
			boolean valid1 = false;
			System.out.println("insert the first number:");
			n1 = sc1.nextInt();
			while(valid1 == false){
				System.out.println("insert operator:");
				System.out.println("(+, -, :, X o ^)");
				op = sc1.next().charAt(0);
				if(op != '+' && op != '-' && op != ':' && op != 'X' && op != 'x' && op != '^'){
					Error();
				} else {
					valid1 = true;
				}
			}
			System.out.println("insert the second number:");
			n2 = sc1.nextInt();
			switch(op){
				case '+':
					res = n1 + n2;
					Oper(" addition ", res, otOp, n1, n2); //ERROR IS HERE
					if(Oper(" addition ", res, otOp, n1, n2) == true){ //In this line, the condition has the same call of the previous line
						otOp = true;
					} else{
						otOp = false;
					}
				break;
				case '-':
					res = n1 - n2;
					Oper(" substraction ", res, otOp, n1, n2); //same here
					if(Oper(" substraction ", res, otOp, n1, n2) == true){ //and here
						otOp = true;
					} else{
						otOp = false;
					}
				break;
				case ':':
					res = n1 / n2;
					Oper(" division ", res, otOp, n1, n2); //^^
					if(Oper(" division ", res, otOp, n1, n2) == true){ //==
						otOp = true;
					} else{
						otOp = false;
					}
				break;
				case 'X':
				case 'x':
					res = n1 * n2;
					Oper(" multiplication ", res, otOp, n1, n2); //^^
					if(Oper(" multiplication ", res, otOp, n1, n2) == true){ //==
						otOp = true;
					} else{
						otOp = false;
					}
				break;
				case '^':
					long pot = 1;
						for (int i = 1; i <= n2; i++){
							pot *= n1;
						}
					res = pot;
					Oper(" power ", res, otOp, n1, n2); //^^
					if(Oper(" power ", res, otOp, n1, n2) == true){ //==
						otOp = true;
					} else{
						otOp = false;
					}
				break;
			}
		}
	}
	static void Error(){
		System.out.println("ERROR, invalid option");
	}
	static boolean Oper(String oper, long res, boolean otOp, long n1, long n2){
		boolean valid2 = false;
		Scanner sc2 = new Scanner(System.in);
		System.out.println("the result of the" + oper + "is " + res);
		if(oper == " division "){
			System.out.println("reminder: " + (n1 % n2));
		}
		System.out.println("any other operation? (y/Y = Yes, n/N = No)");
		char in = sc2.next().charAt(0);
		while(valid2 == false){
			if(in == 'y' || in == 'Y'){
				otOp = true;
				valid2 = true;
			} else if(in == 'n' || in == 'N'){
				otOp = false;
				valid2 = true;
			} else{
				Error();
			}
		} return otOp;
	}
}

Please copy the full contents of the console from when you test the program and paste it here so we can run the test exactly the same way you have.

One problem I see is the code is using 2 Scanner objects. It is better if only one Scanner is used.

How are you trying to debug the code to see why it is not doing what you want? Add some print statements that print the values of variables at all the places where the code is making the wrong decisions based on some variables' contents. The print outs will show you what the computer is seeing when the code is executed and help you see what is wrong in the code.

I think you asked for something like this:

java Calculator

out: insert the first number:

in: (any number in the long range)

out: insert operator:
out: (+, -, :, X o ^)

in: (any operator)

out: insert the second number:

in: (any number in the long range)

out: "the result of the" + operation + "is " + result
out: any other operation? (y/Y = Yes, n/N = No)

in: Y

out: "the result of the" + operation + "is " + result
out: any other operation? (y/Y = Yes, n/N = No)

in: Y

-asks for numbers and operator again-

out: "the result of the" + operation + "is " + result
out: any other operation? (y/Y = Yes, n/N = No)

in: N

out: "the result of the" + operation + "is " + result
out: any other operation? (y/Y = Yes, n/N = No)

in: Y

out: "the result of the" + operation + "is " + result
out: any other operation? (y/Y = Yes, n/N = No)

-asks for numbers and operator again-

out: "the result of the" + operation + "is " + result
out: any other operation? (y/Y = Yes, n/N = No)

in: N

out: "the result of the" + operation + "is " + result
out: any other operation? (y/Y = Yes, n/N = No)

in: N

out: "the result of the" + operation + "is " + result
out: any other operation? (y/Y = Yes, n/N = No)

-program stops-

[...]

out: "the result of the" + operation + "is " + result
out: any other operation? (y/Y = Yes, n/N = No)

in: Y

out: "the result of the" + operation + "is " + result
out: any other operation? (y/Y = Yes, n/N = No)

in: N

out: "the result of the" + operation + "is " + result
out: any other operation? (y/Y = Yes, n/N = No)

-program stops-

If I choose anything, the program ignores my first input and asks me one more time before closing the program or printing "insert the first number:" again.

I tried printing the variables of the program but it just works as it should work.

Please copy the exact text of the console from when you run the program.
The last post does not look like the exact text from when you executed the program. The exact text is important to allow anyone to follow what the code did when it executed. Your edits to the output muddy the waters for seeing what exactly the program did.

Where in the code is this message printed:

out: any other operation? (y/Y = Yes, n/N = No)

For it to be printed 2 times means the method that the print statement is in was called 2 times. Why is that method called 2 times?