Java Code to Find Leap Year Error (Code, Error, and Attempts to Fix Included)

[Jeremiah Waters]

Objective of Code: I need a write a code that will allow for a user to insert a year, and the code will tell them if it is a leap year by dividing it by 4. If the year is a leap year, the code will output the text "[YEAR] is a leap year." If not, it will produce "[YEAR] is NOT a leap year."

Error with the Code (as it is included below): Whenever I run the code, I do get the option to enter the year I want to evaluate. However, once I enter it, nothing happens. I'm not receiving any specific error message. I thought this meant that I needed to change my code in some way to include some sort of message to output a statement like those included above ("[YEAR] is/is NOT a leap year."), but my attempts (included after my code) to fix it haven't worked.

Code (As Is):

The following code is in the main of one class (Main.java).

import static java.lang.System.*; 
import java.util.Scanner;
import static java.lang.Math.*;

public class Main
{
	public static void main( String args[] )
	{
	  
		Scanner keyboard = new Scanner(System.in);
			
		System.out.print("Enter a year ::  ");
	        int year = keyboard.nextInt();
	
	}
}

The following code is in the main of another class (LeapYear.java).

import static java.lang.System.*; 
import java.util.Scanner;
import static java.lang.Math.*;

public class LeapYear
{
	public static String isLeapYear( int year )
	//The String above was originally Boolean, but I changed it because Boolean caused a whole other sling of errors.
	{
	  if (year % 4 == 0)
	    {
	      return(year + "is a leap year.");
	    }
	  return year + "is NOT a leap year.";
	}
}

Attempt to fix 1: I added the statement-

 LeapYear test = new LeapYear (year);
	  test.isLeapYear();
	  System.out.println(test);

To my main in Main.java after-

         

int year = keyboard.nextInt();

Because there was a similar statement included in another batch of code I'm worked on a few weeks ago. However, this change resulted in this error:

exit status 1
Main.java:19: error: constructor LeapYear in class LeapYear cannot be applied to given types;
  	LeapYear test = new LeapYear (year);
  	                ^
  required: no arguments
  found: int
  reason: actual and formal argument lists differ in length
Main.java:20: error: method isLeapYear in class LeapYear cannot be applied to given types;
	  test.isLeapYear();
	      ^
  required: int
  found: no arguments
  reason: actual and formal argument lists differ in length
2 errors

I'm not quite sure what this error means (I'm pretty new to Java), so I just tried something else.

Attempt to fix 2: I deleted the code I added in Attempt to fix 1 and tried to make my return statements-

 if (year % 4 == 0)
	    {
	      return(year + "is a leap year.");
	    }
	  return year + "is NOT a leap year.";

Into statements like-

       

out.println(year + "is a leap year.");

and-

       

out.println (year + "is NOT a leap year.");

But I got the error that I was missing a return statement. I tried adding return to the beginning of the new out.println statements above, but got this error-

exit status 1
LeapYear.java:16: error: incompatible types: void cannot be converted to String
	      return out.println(year + "is a leap year.");
	                        ^
LeapYear.java:18: error: incompatible types: void cannot be converted to String
	  return out.println(year + "is NOT a leap year.");
	                    ^
2 errors

In Conclusion

How can I make my code output the appropriate "[YEAR] is/is NOT a leap year." statements? Thank you!

(I tried to be thorough in my explanation of what I was trying to do/what I tried in order to fix my error, but if I missed something please let me know!)

[Carey Brown]

import static java.lang.System.*; 
import java.util.Scanner;
import static java.lang.Math.*;
 
public class Main
{
    public static void main( String args[] )
    {
       
        Scanner keyboard = new Scanner(System.in);
             
        System.out.print("Enter a year ::  ");
            int year = keyboard.nextInt();
        System.out.println( LeapYear.isLeapYear(year) );
    }
}

Your method isLeapYear() is static to the LeapYear class so you have to call it in a static manner using the class name:

LeapYear.isLeapYear(....)

It returns a String so you have to output that when the method returns.

[Jeremiah Waters]

Thank you Carey!

I made your suggested adjustment, but now I'm receiving this error. What does this mean?

exit status 1
LeapYear.java:16: error: incompatible types: unexpected return value
	      return out.println(year + "is a leap year.");
	                        ^
LeapYear.java:18: error: incompatible types: unexpected return value
	  return out.println(year + "is NOT a leap year.");
	                    ^
Main.java:18: error: 'void' type not allowed here
    System.out.println( LeapYear.isLeapYear(year) );
                                           ^
3 errors

[Carey Brown]

You've posted so many different changes. This is what you had at one point:

if (year % 4 == 0)
       {
         return(year + "is a leap year.");
       }
     return year + "is NOT a leap year.";

In order to help you you need to post the current code in its entirety and any error messages in their entirety.

[Campbell Ritchie]

Weelcome to the Ranch

Jeremiah Waters wrote: . . .

import static java.lang.System.*; 
import java.util.Scanner;
import static java.lang.Math.*;
// ...

You seem to have lots of static imports, but are you actually using them?

The following code is in the main of another class (LeapYear.java).

Please don't go thinking there is anything important about the main method. It is like the Union Flag at the Grand Prix at Silverstone. The Union Flag isn't really important: the cars are the important part. It is there for starting the application but there is nothing important about the main method. More information here.

[code=java:fistline[8]]public static String isLeapYear( int year )
//The String above was originally Boolean, but I changed it because Boolean caused a whole other sling of errors.[/code]

Don't change your code to correct the error messages. Use the error messages to find the error in your code and change the code to correct the errors. A method with a name starting is should usually return a boolean (not a Boolean). So make your method return a boolean, and run your code until you can pass years and get the results true or false. That shouldn't take long. Note what this old style guide says about boolean returns.

Attempt to fix 1: . . .

Program to the design of your application, not to get rid of the compiler errors. You have two options. You can design a class representing a year, in which case it would have a year number as a field and a method to show whether it is a leap year. That is one option. You would not have a method taking a year number to show whether it is a leap year. That means you have to create a standard Java® class and make objects from it.
The alternative, which is less object‑oriented, would be not to have any fields and make all method static as you are already trying. You don't need any objects of the LeapYear class.

[Jeremiah Waters]

Thank you Carey! Sorry for the delay!

Here is my current code:

import static java.lang.System.*; 
import java.util.Scanner;
import static java.lang.Math.*;

public class Main
{
	public static void main( String args[] )
	{
	  
		Scanner keyboard = new Scanner(System.in);
			
    System.out.print("Enter a year ::  ");
    int year = keyboard.nextInt();
    System.out.println( LeapYear.isLeapYear(year) );
	}
}

and

import static java.lang.System.*; 
import java.util.Scanner;
import static java.lang.Math.*;

public class LeapYear
{
	public static void isLeapYear( int year )
	//The "String" above was originally "Boolean,"" but I changed it because it caused a whole other sling of errors.
	{
	  if (year % 4 == 0)
	    {
	      return out.println(year + "is a leap year.");
	    }
	  return out.println(year + "is NOT a leap year.");
	}
}

[Dave Tolls]

I think Carey's suggesting you go back to your original posted code.

[Jeremiah Waters]

Thank you Dave and Carey! It's working now!

[Carey Brown]

Jeremiah Waters wrote:Thank you Dave and Carey! It's working now!

I'm glad you got it to work. Very good.
It would be appreciated if you posted your final working code here so that others may learn from it.

[Jeremiah Waters]

For anyone who's experiencing a similar issue, here's my final code!

This code is in the main of class Main.java:

import static java.lang.System.*; 
import java.util.Scanner;
import static java.lang.Math.*;

public class Main
{
	public static void main( String args[] )
	{
	  
		Scanner keyboard = new Scanner(System.in);
			
    System.out.print("Enter a year ::  ");
    int year = keyboard.nextInt();
    System.out.println( LeapYear.isLeapYear(year) );
	}
}

This code is in the main of class LeapYear.java:

import static java.lang.System.*; 
import java.util.Scanner;
import static java.lang.Math.*;

public class LeapYear
{
	public static String isLeapYear( int year )
	{
	  if (year % 4 == 0)
	    {
	      return year + " is a leap year.";
	    }
	  return year + " is NOT a leap year.";
	}
}

Best of luck!