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Java Program to display curent month calender.

Java Code Example — Utility Programs

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Java Program to display curent month calender.

Objective

Write a Java program to display the calendar for the current month on the console.

Algorithm / Approach

  1. Instantiate a GregorianCalendar.
  2. Extract the current day, month, and the first day of the week.
  3. Set the calendar to the 1st day of the month using d.set(Calendar.DAY_OF_MONTH, 1).
  4. Print the Days of the Week header using DateFormatSymbols.
  5. Print empty spaces until the start day of the week is reached.
  6. Loop through the days, printing each one, adding an asterisk if it is the current day, and breaking to a new line at the end of the week.
ShowCalendar.java 
import java.util.*;
import java.text.*;
import static java.util.Calendar.*;
class ShowCalendar {
 public static void main(String[] args) {
  GregorianCalendar d;
  d = new GregorianCalendar();
  int today = d.get(DAY_OF_MONTH);
  int month = d.get(MONTH);
  int weekFirstDay = d.getFirstDayOfWeek();
  d.set(Calendar.DAY_OF_MONTH, 1);
  int startDay = d.get(DAY_OF_WEEK);
  DateFormatSymbols ob;
  ob = new DateFormatSymbols();
  String [] days = ob.getShortWeekdays();
  for(int i=1;i< days.length;i++){
   System.out.printf("%-4s",days[i]);
  }
  System.out.println("");
  for(int i=1;i< startDay;i++){
   System.out.print("   ");
  }
  while(true){
   int day = d.get(DAY_OF_MONTH);
   System.out.printf("%3d",day);
   d.add(DAY_OF_MONTH,1);
   if(day==today)
    System.out.print("*");
   else
    System.out.print(" ");
   if(d.get(DAY_OF_WEEK)==weekFirstDay)
    System.out.println("");
   if(month!=d.get(MONTH))break;
  }
  System.out.println("");
 }
}

Expected Output

Sun Mon Tue Wed Thu Fri Sat
                          1
  2   3   4   5   6   7   8
  9  10  11  12  13* 14  15
 16  17  18  19  20  21  22
 23  24  25  26  27  28  29
 30

Explanation of the Program

  • This program combines complex Date manipulation with precise Console formatting.
  • The GregorianCalendar class provides advanced calendar calculations (like figuring out what day of the week a specific date falls on). We mathematically shift the cursor based on the week layout to draw a standard wall calendar.

Complexity

Time Complexity O(1)
Space Complexity O(1)
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