What's wrong with this Java program regarding TimeUnit Day conversion?

Question

When I code like this I get no error :-

import java.util.Date;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.concurrent.TimeUnit;


  public class DateDifference{
      public static void main(String[] main){
         String str = "20121401092958";
        /* TimeUnit spanInDays = */getDateDiff(str);
         //System.out.println(spanInDays);
      }

      public static void getDateDiff(String str ){
           DateFormat dateFormat = new SimpleDateFormat("yyyyMMddHHmmss"); 
           Date currentDate = new Date();
           Date givenDate = null;
           Date d2 = null;
           try{
                givenDate = dateFormat.parse(str);

                long diff = currentDate.getTime() - givenDate.getTime();

                System.out.println("Days "+ TimeUnit.DAYS.convert(diff, TimeUnit.MILLISECONDS)); 
           }catch(Exception e){
              e.printStackTrace();
           }
      }
  }

but when I code it like this :-

import java.util.Date;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.concurrent.TimeUnit;


  public class DateDifference{
      public static void main(String[] main){
         String str = "20121401092958";
         TimeUnit spanInDays = getDateDiff(str);
         System.out.println(spanInDays);
      }

      public static TimeUnit getDateDiff(String str ){
           DateFormat dateFormat = new SimpleDateFormat("yyyyMMddHHmmss"); 
           Date currentDate = new Date();
           Date givenDate = null;
           Date d2 = null;
           try{
                givenDate = dateFormat.parse(str);

                long diff = currentDate.getTime() - givenDate.getTime();

                return TimeUnit.DAYS.convert(diff, TimeUnit.MILLISECONDS); 
           }catch(Exception e){
              e.printStackTrace();
           }
      }
  }

I get Compilation Error

DateDifference.java:24: error: incompatible types: long cannot be converted to TimeUnit
                                return TimeUnit.DAYS.convert(diff, TimeUnit.MILLISECONDS);
                                                            ^
1 error

How to fix that?

Answer 1

The compiler is saying that the return type of the method is not what it expected; you declared it as TimeUnit but you're returning a value of type long .

Since that makes sense (you are returning a long , not a definition of a TimeUnit ), you should adjust the return type:

public static long getDateDiff(String str) {

Answer 2

Your method is

public static TimeUnit ...

So your method has to return type TimeUnit . What you have it returning is a long

TimeUnit.Days.convert(diff, TimeUnit.MILLISECONDS) is type long

Just change the return type or what it is returning to match.

Hope this helps.