How to use reusable function - Android, Java

Question

I implemented small if-else part to get First three letters of the month when Calendar instance = Calendar.getInstance(); retrieves integer value of the month. I wanna use it as a reusable function. I've tried by creating another java file but it want works. Can anyone tell me how can I use it?

public class MstrMonth {

    public MstrMonth() {}

    public static String getCurrentMonth(String currentMonth) {

        Calendar instance = Calendar.getInstance();
        int mMonth = instance.get(Calendar.MONTH) + 1;

        if(mMonth == 1){
            currentMonth = "JAN";
        }else if (mMonth == 2){
            currentMonth = "FEB";
        }else if (mMonth == 3){
            currentMonth = "MAR";
        }else if (mMonth == 4){
            currentMonth = "APR";
        }else if (mMonth == 5){
            currentMonth = "MAY";
        }else if (mMonth == 6){
            currentMonth = "JUN";
        }else if (mMonth == 7){
            currentMonth = "JUL";
        }else if (mMonth == 8){
            currentMonth = "AUG";
        }else if (mMonth == 9){
            currentMonth = "SEP";
        }else if (mMonth == 10){
            currentMonth = "OCT";
        }else if (mMonth == 11){
            currentMonth = "NOV";
        }else if (mMonth == 12){
            currentMonth = "DEC";
        }
        return currentMonth;
    }
}

In Main activity;

String currentMonth;
MstrMonth.getCurrentMonth(currentMonth);

I want get Month code in here but it gives null value.

Answer 1

Try this.

public static String getCurrentMonth() {
    Calendar instance = Calendar.getInstance();
    return instance.getDisplayName(
        Calendar.MONTH, Calendar.SHORT, Locale.ENGLISH).toUpperCase();
}

public static void main(String[] args) throws Exception {
    String currentMonth = getCurrentMonth();
    System.out.println(currentMonth);
}

output:

NOV