Project # 4 and Calculator

Code

    ///Name: Tim Gibson
    ///Period: 6
    ///Project Name: Calculator
    ///File Name: Calculator.java
    ///Date Finished: 12/4/15
        
    import java.util.Scanner;
    
    public class Calculator
    {
        public static void main ( String[] args )
        {
            Scanner kb = new Scanner(System.in);
            
            System.out.println( "Hello, welcome to the calculator. \nPlease input whether angles are in \"degrees\" or \"radians\"" );
            
            String a, b, c;
            boolean a1, b1, c1; //corresponds to each input
            double a2, b2, c2;
            a2 = 1;// they have to be initialized
            a2 = 1;// they have to be initialized
            b2 = 1;
            c2 = 1; 
            do
            {
                System.out.print(">");
                a = kb.next();
                b = kb.next();
                c = kb.next();
                
                a1 = Numeric.isNumeric(a);
                b1 = Numeric.isNumeric(b);
                c1 = Numeric.isNumeric(c);
                
                if ( a1 == true ) //converting everything to doubles if they're numbers
                    a2 = Double.parseDouble(a);
                if ( b1 == true )
                    b2 = Double.parseDouble(b);
                if ( c1 == true )
                    c2 = Double.parseDouble(c);
                
                
                if ( a1 == false && b1 == true ) // trig functions
                {
                    if ( a.equals("sin"))
                        System.out.println(sin(b2,c));
                    else if ( a.equals("cos"))
                        System.out.println(cos(b2,c));
                    else if ( a.equals("tan"))
                        System.out.println(tan(b2,c));
                }
                else if ( b.equals("+") && a2 != 0)
                    System.out.println(add(a2,c2));
                else if ( b.equals("-") && a2 != 0)
                    System.out.println(subt(a2,c2));
                else if ( b.equals("^") && a2 != 0)
                    System.out.println(exp(a2,c2));
                else if ( b.equals("/") && a2 != 0)
                    System.out.println(div(a2,c2));
                else if ( b.equals("*") && a2 != 0)
                    System.out.println(mult(a2,c2));
                else if ( b.equals("!") && a2 != 0)
                    System.out.println(fact(a2));
                else if ( a2 == 0 )
                    System.out.println( "Bye" );
                else 
                    System.out.println( "Error. Try Again"); 
            } while ( a2 != 0 );
        }
                                       
        public static double add( double a, double b )
        {
            double c = a + b;
            
            return c;
        }
        
        public static double subt( double a, double b )
        {
            double c = a - b;
            return c;
        }
                                       
        public static double exp( double a, double x )//x is exponent
        {
            double c = 1;
            for ( int n=1;n<=x;n++)
            {
                c*=a;
            }
            return c;
        }
        
        public static double div( double a, double b )
        {
            double c = a / b;
            return c;
        }
        
        public static double mult( double a, double b )
        {
            double c = a * b;
            return c;
        }
        
        public static double fact( double a )
        {
            double b = a - 1;
            for ( double n = b; n > 0; n -= 1)
            {
                a *= n;
            }
            return a;
        }
                        
        public static double sin( double a, String b )
        {
            double c = 0; //intializing c
            double r; //radians
            if ( b.equals("radians"))
                c = Math.sin(a);
            else if ( b.equals("degrees"))
            {
                r = ( a * Math.PI ) / 180;
                c = Math.sin(r);
            }
            return c;
        }
                                       
        public static double cos( double a, String b )
        {
            double c = 0; //intializing c
            double r; //radians
            if ( b.equals("radians"))
                c = Math.cos(a);
            else if ( b.equals("degrees"))
            {
                r = ( a * Math.PI ) / 180;
                c = Math.cos(r);
            }
            return c;
        }
                                       
        public static double tan( double a, String b ) 
        {
            double c = 0; //intializing c
            double r; //radians
            if ( b.equals("radians"))
                c = Math.tan(a);
            else if ( b.equals("degrees"))
            {
                r = ( a * Math.PI ) / 180;
                c = Math.tan(r);
            }
            return c;
        }
    }
        

Picture of the output