java - Modifying else if and | operators

Question

I have this snippet of code and want to know if exist way to make it much more readable?

My code:

     public String getMonthName()
{
    if (1 == this.monthNumber) {
        monthName = "January";
    } else if (2 == this.monthNumber) {
        monthName = "February";
    } else if (3 == this.monthNumber) {
        monthName = "March";
    } else if (4 == this.monthNumber) {
        monthName = "April";
    } else if (5 == this.monthNumber) {
        monthName = "May";
    } else if (6 == this.monthNumber) {
        monthName = "June";
    } else if (7 == this.monthNumber) {
        monthName = "July";
    } else if (8 == this.monthNumber) {
        monthName = "August";
    } else if (9 == this.monthNumber) {
        monthName = "September";
    } else if (10 == this.monthNumber) {
        monthName = "Oktober";
    } else if (11 == this.monthNumber) {
        monthName = "November";
    } else if (12 == this.monthNumber) {
        monthName = "December";
    }

    return monthName;
}

/**
 * Gets the number of days in this month
 * @return the number of days in this month in a non-leap year
 */
public int getNumberOfDays()
{
    int numberOfDays;
    if (monthNumber == 1 || monthNumber == 3 || monthNumber == 5 || monthNumber == 7 || monthNumber == 9 || monthNumber == 11) {
        numberOfDays = 31;
    } else if (monthNumber == 4 || monthNumber == 6 || monthNumber == 8 || monthNumber == 10 || monthNumber == 12) {
        numberOfDays = 30;
    } else {
        numberOfDays = 28;
    }

    return numberOfDays;
}
}

How better way to refactoring code? Make it much more readable.

score 3 · Accepted Answer

Use enum

public enum Month
{
  JANUARY( "January", 31 ),
  FEBRUARY( "February", 28 ),
  ...
  DECEMBER( "December", 31 );

  private String monthName;
  private int numOfDays;

  private Month ( String monthName, int numOfDays )
  {
    this.monthName = monthName;

    this.numOfDays = numOfDays;
  }

  public String getDisplayName ( )
  {
    return monthName;
  }

  public int getNumOfDays ( )
  {
    return numOfDays;
  }
}

score 1 · Accepted Answer

Make an array that stores all the names. If this.monthNumber is between 1 and 12, read the name out of the array.

score 1 · Accepted Answer

Not sure if this is exactly what you were asking for, but it's a start! Comment if you would like it in some other way.

public string getMonthName(int nbr){
    String[] months = {"January", "February", "Mars", "April", "May", "June", "July", "August", "September", "Oktober", "November", "December"}:    
    return months[nbr-1];
}

public int nbrOfDays(int nbr){
    int[] nbrOfDays= {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    return nbrOfDays[nbr-1];
}

EDIT: fixed the "index 0 issue".

score 1 · Accepted Answer

public String getMonthName(){
     switch (this.monthNumber) {
                case 1:  monthString = "January";
                    break;
                case 2:  monthString = "February";
                    break;
                case 3:  monthString = "March";
                    break;
                case 4:  monthString = "April";
                    break;
                case 5:  monthString = "May";
                    break;
                case 6:  monthString = "June";
                    break;
                case 7:  monthString = "July";
                    break;
                case 8:  monthString = "August";
                    break;
                case 9:  monthString = "September";
                    break;
                case 10: monthString = "October";
                    break;
                case 11: monthString = "November";
                    break;
                case 12: monthString = "December";
                    break;
                default: monthString = "Invalid month";
                    break;
      }
      return monthString;
}

score 1 · Accepted Answer

You should use the Calendar class, it was provided to save you from all this extra branching. You also won't have to determine if it is a Leap Year, the API will take of that for you.

final String[] months = new String[]{ "January", "February", ... };

public String getMonthName() {
    return months[Calendar.getInstance().get(Calendar.MONTH)];
}

public int getNumberOfDays() {
    return Calendar.getInstance().getActualMaximum(Calendar.DAY_OF_MONTH);
}

score 0 · Accepted Answer

String[] months = String[] {"Jan", "Feb", ... , "Dec"};

String monthName = months[monthNumber - 1];

score 0 · Accepted Answer

Use enums. Months and its orderung/number and days don't change, so months are quite a good example when and how to use them. Let the enum have an int numberOfDays and if you need a monthNumber. Though you need to get into enums you will gain a lot as you can reuse your code and probably can omit your if/switch statement as well.

score 0 · Accepted Answer

Make two arrays for month and number of date per month. both are size of 12.

in month array put name of the month in order from index 0 to 11 and put number of days in order to from index 0 to 11. now you can retrieve data by index.

score 0 · Accepted Answer

public String getMonthName(){
     switch (monthNumber) {
         case 1:  return "January";
         case 2:  return "February";
         case 3:  return "March";
         case 4:  return "April";
         case 5:  return "May";
         case 6:  return "June";
         case 7:  return "July";
         case 8:  return "August";
         case 9:  return "September";
         case 10: return "October";
         case 11: return "November";
         case 12: return "December";
         default: return "Invalid month";
      }
}

java - Modifying else if and | operators

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