如果还有错误，我不理解此错误

Question

I don't understand this error is it logical error or something else here is the coding " this program should convert riyal to currency that is chosen by the user using multiway if-else

import java.util.Scanner;

public class Convert
{
    public static void main (String[] args)
    {
        Scanner kb= new Scanner (System.in);

        double riyal, c;
        int opp;

        System.out.println("Please enter the amount of money in Riyal: ");
        riyal= kb.nextDouble();

        System.out.println("Enter the currency option(1- Dollar, 2- Euro, 3- Yen): ");
        opp= kb.nextInt();

        if(opp==1)

            c=riyal*0.267;
        System.out.print(riyal+" Riyals is converted to "+c" Dollars");

        else if (opp==2)

            c=riyal*0.197;  
            System.out.print(riyal+" Riyals is converted to "+c" Euros");

         else if (opp==3)

            c=riyal*0.27.950;
          System.out.print(riyal+" Riyals is converted to "+c" Yens");

         else
         {
            System.out.println("Invalied opption");
        }
    }
}

Error message:

error: illegal start of expression
error: 'else' without 'if'
error: ';' expected
error: ')' expected

The program that I'm using is Jcreator

Answer 1

You aren't marking the start and end the bodies of your if statements - wihch means they're just single statements. You've currently effectively got:

if(opp==1) {
    c=riyal*0.267;
}
System.out.print(riyal+" Riyals is converted to "+c" Dollars");
else if (opp==2)

As you can see, that else doesn't "belong" to any if block. I'd strongly recommend that you always use braces, even for single-statement if bodies:

if(opp==1) {
    c=riyal*0.267;
    System.out.print(riyal+" Riyals is converted to "+c" Dollars");
} else if (opp==2) {
    ...
} // etc

Note that if you get your IDE to format your code, this should all become rather clearer. The indentation that the IDE will apply will show you how things are actually being understood...

Answer 2

You are supposed to use curly braces if your if blocks have more than a single statement :

if(opp==1) {
    c=riyal*0.267;
    System.out.print(riyal+" Riyals is converted to "+c" Dollars");
} else if (opp==2) {    
    c=riyal*0.197;  
    System.out.print(riyal+" Riyals is converted to "+c" Euros");       
} else if (opp==3) {             
    c=riyal*0.27.950;
    System.out.print(riyal+" Riyals is converted to "+c" Yens"); 
} ... and so on ...

When you write it without the braces, it's equivalent to:

if(opp==1) {
    c=riyal*0.267;
}
System.out.print(riyal+" Riyals is converted to "+c" Dollars");

else if (opp==2)

so the else if is not related to any if .

Answer 3

if , else , and other flow control statements operate on the one statement that follows them. When you have more than one, you use a block ( {} ):

if(opp==1) {
    c=riyal*0.267;
    System.out.print(riyal+" Riyals is converted to "+c" Dollars");
}
else if (opp==2) {
// ...