Switch

Hey guys working on a simple switch program but not exactly a 100% if i can convert my what was a if statement into a switch or not. Any help would be awesome Thanks!

Code :

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import java.util.Scanner;
 
public class math
{
  public static void main(String[] args)
{
 
 
Scanner input = new Scanner(System.in);
 
System.out.println(" Please select one of these options.");    
System.out.println(" 1. Press A to add three numbers ");
System.out.println(" 2. Press S to subtract two numbers ");
System.out.println(" 3. Press M to multiply by three numbers ");
System.out.println(" 4. Press D to divide by two numbers ");
System.out.println(" 5. Press O to modulus two numbers ");
System.out.println(" 6. Press E to quit the program ");
System.out.println(" ");
 
int option= input.nextInt();
 
 
    switch (option)
    {
    case 'A': {
      addition (); }
    break;
      case 'S': {
      subtract (); }
      break;
    case 'M': {
      multiply (); }
    break;
      case 'D': {
      divide (); }
      break;
      case 'O': {
      modulus (); }
      break;
      case 'E': {
      quit ();}
      break;
      default: 
 
      System.out.println("Not a option"); }
 
    }
 
 
    public static void addition(){
             Scanner input = new Scanner( System.in );
             float number1;
             float number2;
             float number3;
             float sum;
 
      System.out.printf( "Enter first integer: " );
      number1 = input.nextInt();
      System.out.printf( "Enter second integer: " );
      number2 = input.nextInt();
      System.out.printf( "Enter Third integer: " );
      number3 = input.nextInt();
 
             sum = number1 + number2 + number3;
             System.out.printf( "Sum equals %f\n", sum);
    }
    public static void subtract(){
             Scanner input = new Scanner( System.in );
             float number1;
             float number2;
             float difference;
 
      System.out.printf( "Enter number to be subtracted: " );
      number1 = input.nextInt();
      System.out.printf( "Enter integer to subtract: " );
      number2 = input.nextInt();
 
 
             difference = number1 - number2;
             System.out.printf( "The difference is %f\n", difference);
 
    }
    public static void multiply(){
            Scanner input = new Scanner( System.in );
             float number1;
             float number2;
             float number3;
             float product;
 
      System.out.printf( "Enter first integer to multiply: " );
      number1 = input.nextInt();
      System.out.printf( "Enter second integer: " );
      number2 = input.nextInt();
      System.out.printf( "Enter Third integer: " );
      number3 = input.nextInt();
 
      product = number1 * number2 * number3;
      System.out.printf( "The product is %f\n", product);
 
    }
 
    public static void divide(){
          Scanner input = new Scanner( System.in );
           float number1;
           float number2;
           float dividen;
 
      System.out.printf( "Enter first integer: " );
      number1 = input.nextInt();
      System.out.printf( "Enter second integer: " );
      number2 = input.nextInt();
 
      dividen = number1 / number2;
      System.out.printf( "The dividen equals %f\n", dividen);
 
    }
 
    public static void modulus(){
         Scanner input = new Scanner ( System.in );
          float number1;
          float number2;
          float sum;
 
        System.out.printf( "Enter first integer: " );
        number1 = input.nextInt();
        System.out.printf( "Enter second ineger: " );
        number2 = input.nextInt();
 
        sum = number1 % number2;
        System.out.printf( "The answer equals %f\n", sum);
 
    }
 
    public static void quit(){
      System.out.printf( "Thank you for trying to use the program.");
      return; 
 
    }
 
  }

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Can you explain what the problem is?

The message printed for the default: should include the invalid option's value.

Sorry that's a good point didn't really specify what the problem was. The program reads the input but once it gets past that i can't get the program to start the lower operations. I'm using Dr.java this is the error

Quote:

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java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at question4.main(question4.java:21)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknow n Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Un known Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at edu.rice.cs.drjava.model.compiler.JavacCompiler.ru nCommand(JavacCompiler.java:272)

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Quote:

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java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at question4.main(question4.java:21)

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The call to nextInt() at line 21 is trying to read an int value from the keyboard but the user is entering something that is not a numeric value. Use the next() or nextLine() method if you want to read a String not a number.

Thank you, this is kind of making me feel like i may not be able to go about it in this way. It makes my option not work in the string anymore. Says that i can not make option a variable, would i have to convert a Int to a String which i have read is not a simple solution, or is there another way?

To convert an int to a String just use Integer.parseInt(number); (Integer (Java Platform SE 7 ))

Try to be consistent. Nearly all input from GUI's are strings first and then converted.

Quote:

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To convert an int to a String just use Integer.parseInt(number)

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Wrong. The parseInt() method converts a String to an int.
Read the String class's API doc for methods to convert an int to a String.

With Java 1.7 switch statements will work with Strings.

Thanks for locating my error. If you read the rest of my reply, you will see that I'm suggesting he start with a string, and then convert since Java GUIs take this approach.

Thanks a lot Norm really helped me figure that out. Was way easier then i was trying to make it, forgot to come back and thank you guys.


This is what i ended up with.

Quote:

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Scanner input = new Scanner( System.in );
String aString = input.next();
char choice = aString.charAt(0);


switch (choice)
{
case 'A': {
addition (); }

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