public class Calculator {
	private int operand1;
	private int operand2;
	private char operator1;
	private double result;
	
	public double calculate(char op, int num1, int num2)
	{
		operand1 = num1;
		operand2 = num2;
		operator1 = op;
		if (operator1 == '+')
		{
			addition();
		}
		else if (operator1 == '-')
		{
			subtraction();
		}
		else if (operator1 == '*')
		{
			multiplication();
		}
		else if (operator1 == '/')
		{
			division();
		}
		return result;
	}
	public void addition()
	{
		result = operand1 + operand2; 	
	}
	public void subtraction()
	{
		result = operand1 - operand2;
	}
	public void multiplication()
	{
		result = operand1 * operand2;
	}
	public void division()
	{
		result = operand1 / operand2;
	}

}

Java로 만든 계산기에서 계산기 class 부분의 구현