Errors somewhere in code

Question

I'm 100% new to Java and am currently doing a course in it. I'm doing a mock up program that tests a users input against a pre-defined code I.E. a password (The numbers from the program Lost), however I am running into difficulties (see below) any help would be greatly appreciated. The main error I'm getting is with the if else statement...

import java.util.Scanner;

public class Lost 
{
   public static void main( String[] args ) 
   {
       String  myNumber;
       myNumber = "4815162342" ; 

      // create Scanner to obtain input from command window
      Scanner input = new Scanner( System.in );


      // prompt user for input and obtain value from user
      System.out.print( "Enter numbers..." );


      // if...else is nested

      if ( result == myNumber );
           // if result numbers,
          System.out.print( "...You've just saved the world for now!!" );
      else
          System.out.print( "BOOM!!!!" );


  } // end main
} // end class Lost

 // put notes here:

Your `if`-statement is terminated, your input is never read and your `result` never initialized.. have you thought about trying out an IDE with compiler warnings yet? — kasoban, Oct 20 '15 at 11:22
Possible duplicate of [How do I compare strings in Java?](http://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java) — weston, Oct 20 '15 at 11:28
So you just banged all this out before running it. Build it up bit by bit. — weston, Oct 20 '15 at 11:29
@weston: Probably not, this seems more like a syntax problem. The `String` comparison is also a problem of course. — Keppil, Oct 20 '15 at 11:29
@Keppil OK, well If I could change reason I'd change to close as simple typographical error. — weston, Oct 20 '15 at 11:31
@c1jericho Take a look at my solution below. You can accept one solution which helps you most by clicking on the hollow tick beside the answer. You get 2 rep in return. — user3437460, Oct 20 '15 at 11:57

Manos Nikolaidis · Answer 1 · 2015-10-20T11:33:36.010

Your code has the following issues :

if ( result == myNumber ); the ; at the end results in an empty body for the if statement. That's why you get an error for else without if. Delete the ;
result is not defined in your code
You are comparing String variables with ==. That will compare if the references are the same. If you want to compare the contents of the String use
```
if (result.equals(myNumber))
```
You seem to be missing the part that reads user input. It will look something like
```
String result = "";
if (input.hasNextLine())
    result = input.nextLine();
```

PRINCE GUPTA · Answer 2 · 2015-10-20T11:51:02.177

Make changes in your code as

import java.util.Scanner;

public class Lost {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

         String  myNumber;
           myNumber = "4815162342" ; 

          // create Scanner to obtain input from command window

          System.out.print( "Enter numbers..." );

          Scanner input = new Scanner( System.in );

          String result = input.next();


          // prompt user for input and obtain value from user



          // if...else is nested

          if ( result.equals(myNumber) )
               // if result numbers,
              System.out.print( "...You've just saved the world for now!!" );
          else
              System.out.print( "BOOM!!!!" );

    }

}

user3437460 · Answer 3 · 2015-10-20T13:41:11.427

This is what you can do:

import java.util.Scanner;
public class Lost 
{
    public static void main( String[] args ) 
    {
        String myNumber = "4815162342"; 
        Scanner scn= new Scanner(System.in);

        System.out.print("Enter numbers...");
        String result = scn.nextLine();    //receive input with string (Line 10)

        if (result.equals(myNumber))       //compare strings (input vs myNumber)
            System.out.println("...You've just saved the world for now!!");
        else
          System.out.println("BOOM!!!!");
  }
}

If you choose to receive the input numbers with integer, you will be using scn.nextInt() or Integer.parseInt(scn.nextLine()) at line 10, and comparison of result against muNumber will be (result == myNumber) instead of result.equals(myNumber).

As of now, for your basic understanding, when comparing primitives such as int, you use ==. When comparing objects and Strings, use .equals().

Is this code block supposed to be a valid solution for OP's problem? If yes: have you tested it? — Tom, Oct 20 '15 at 13:17

score 0 · Answer 4 · answered Oct 20 '15 at 11:19

Get rid of the semi-colon behind the following line:

if ( result == myNumber );

You might want to get used to enclosing single-statement ifs in curly braces as well. I find that it's less error-prone when you need to add multiple statements to such a branch when the braces are already there.

Errors somewhere in code

4 Answers4