Error message: operator < cannot be applied to boolean,int

Question

I´m new to programming, and are doing som exercices. In this exercice I am supposed to write a program that reads in three numbers from the user of the program. The program is supposed to find the smallest number, and print which one is the smallest number. Here is my code:

import javax.swing.JOptionPane;

public class Smallestnumber
{
  public static void main( String args[] )
    {
    // Defining variables:
    String firstnumberstring;
    String secondnumberstring;
    String thirdnumberstring;
    String result;
    int firstnumber;
    int secondnumber;
    int thirdnumber;

    // Making input frames:
    firstnumberstring = JOptionPane.showInputDialog( "Write first number!" );
    secondnumberstring = JOptionPane.showInputDialog( "Write second number!");
    thirdnumberstring = JOptionPane.showInputDialog( "Write third number!" );

    // Converting stringvalues to int values:
    firstnumber = Integer.parseInt( firstnumberstring );
    secondnumber = Integer.parseInt( secondnumberstring );
    thirdnumber = Integer.parseInt( thirdnumberstring );

    // Initialising printstring to an empty string:
    result = "";

    if ( firstnumber < secondnumber < thirdnumber )
    result = firstnumber + " is the smallest number!";

    if ( firstnumber < thirdnumber < secondnumber )
    result = firstnumber + " is the smallest number!";

    if ( secondnumber < firstnumber < thirdnumber )
    result = secondnumber + " is the smallest number!";

    if ( secondnumber < thirdnumber < firstnumber )
    result = secondnumber + " is the smallest number!";

    if ( thirdnumber < firstnumber < secondnumber )
    result = thirdnumber + " is the smallest number!";

    if ( thirdnumber < secondnumber < firstnumber )
    result = thirdnumber + " is the smallest number!";

    // Making conclusion box:
    JOptionPane.showMessageDialog( null, result, "Conclusion:", JOptionPane.INFORMATION_MESSAGE );

    } // End of main method
} // End of class Smallestnumber

And here is the error messages:

Smallestnumber.java:29: operator < cannot be applied to boolean,int
    if ( firstnumber < secondnumber < thirdnumber )
                                    ^
Smallestnumber.java:32: operator < cannot be applied to boolean,int
    if ( firstnumber < thirdnumber < secondnumber )
                                   ^
Smallestnumber.java:35: operator < cannot be applied to boolean,int
    if ( secondnumber < firstnumber < thirdnumber )
                                    ^
Smallestnumber.java:38: operator < cannot be applied to boolean,int
    if ( secondnumber < thirdnumber < firstnumber )
                                    ^
Smallestnumber.java:41: operator < cannot be applied to boolean,int
    if ( thirdnumber < firstnumber < secondnumber )
                                   ^
Smallestnumber.java:44: operator < cannot be applied to boolean,int
    if ( thirdnumber < secondnumber < firstnumber )
                                    ^
6 errors

How can I get the program to work?

Solution

You can't do thirdnumber < secondnumber < firstnumber in Java, as it interprets it as (thirdnumber < secondnumber) < firstnumber, comparing true or false to the number.

What you want is to combine two conditions like this:

if ( firstnumber < secondnumber && secondnumber < thirdnumber )
result = firstnumber + " is the smallest number!";