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Editorial Team
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Asked: 2026-06-12T09:32:09+00:00

Okay, so I have this code, it prompts a month and a year from

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Okay, so I have this code, it prompts a month and a year from the user and prints the calendar for that month. I’m having some problems though.

  1. the HTML font editing only affects the month.
  2. the days of the week are not aligned in columns correctly.

Thanks!

package calendar_program;

import javax.swing.JOptionPane;

public class Calendar {

public static void main(String[] args) {
    StringBuilder result=new StringBuilder();

    // read input from user
    int year=getYear();
    int month=getMonth();

    String[] allMonths={
            "", "January", "February", "March", "April", "May", "June",
            "July", "August", "September", "October", "November", "December"
    };

    int[] numOfDays= {0,31,28,31,30,31,30,31,31,30,31,30,31};

    if (month == 2 && isLeapYear(year)) numOfDays[month]=29;

    result.append("    "+allMonths[month]+ "  "+ year+"\n"+" S  M  Tu  W Th  F  S"+"\n");

    int d= getstartday(month, 1, year);

    for (int i=0; i<d; i++){
        result.append("    ");
                // prints spaces until the start day
    }
    for (int i=1; i<=numOfDays[month];i++){
        String daysSpace=String.format("%4d", i);
        result.append(daysSpace);
        if (((i+d) % 7==0) || (i==numOfDays[month])) result.append("\n");
    }
    //format the final result string
    String finalresult= "<html><font face='Arial'>"+result; 
    JOptionPane.showMessageDialog(null, finalresult);
}

//prompts the user for a year
public static int getYear(){
    int year=0;
    int option=0;
    while(option==JOptionPane.YES_OPTION){
        //Read the next data String data
        String aString = JOptionPane.showInputDialog("Enter the year (YYYY) :");
        year=Integer.parseInt(aString);
        option=JOptionPane.NO_OPTION;
    }
    return year;
}

//prompts the user for a month
public static int getMonth(){
    int month=0;
    int option=0;
    while(option==JOptionPane.YES_OPTION){
        //Read the next data String data
        String aString = JOptionPane.showInputDialog("Enter the month (MM) :");
        month=Integer.parseInt(aString);
        option=JOptionPane.NO_OPTION;
    }
    return month;
}

//This is an equation I found that gives you the start day of each month
public static int getstartday(int m, int d, int y){
    int year = y - (14 - m) / 12;
    int x = year + year/4 - year/100 + year/400;
    int month = m + 12 * ( (14 - m) / 12 ) - 2;
    int num = ( d + x + (31*month)/12) % 7;
    return num;
}

//sees if the year entered is a leap year, false if not, true if yes
public static boolean isLeapYear (int year){
    if ((year % 4 == 0) && (year % 100 != 0)) return true;
    if (year % 400 == 0) return true;
    return false;
}
}
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1 Answer

  1. Editorial Team

    Here’s a rather stupid idea.

    Rather then formatting your results using spaces, which may be affected by variance in the individual font widths of a variable width font…use a HTML table instead, or a JTable, or JXMonthView from the SwingX project

    HTML Table

    enter image description here

    String dayNames[] = {"S", "M", "Tu", "W", "Th", "F", "S"};
result.append("<html><font face='Arial'>");
result.append("<table>");
result.append("<tr>");
for (String dayName : dayNames) {
    result.append("<td align='right'>").append(dayName).append("</td>");
}
result.append("</tr>");
result.append("<tr>");
for (int i = 0; i < d; i++) {
    result.append("<td></td>");
}
for (int i = 0; i < numOfDays[month]; i++) {
    if (((i + d) % 7 == 0)) {
        result.append("</tr><tr>");
    }
    result.append("<td align='right'>").append(i + 1).append("</td>");
}
result.append("</tr>");
result.append("</table>");

result.append("</html>");

    JTable Example

    enter image description here

    MyModel model = new MyModel();

List<String> lstRow = new ArrayList<String>(7);
for (int i = 0; i < d; i++) {
    lstRow.add("");
}
for (int i = 0; i < numOfDays[month]; i++) {
    if (((i + d) % 7 == 0)) {
        model.addRow(lstRow);
        lstRow = new ArrayList<String>(7);
    }
    lstRow.add(Integer.toString(i + 1));
}

if (lstRow.size() > 0) {
    while (lstRow.size() < 7) {
        lstRow.add("");
    }
    model.addRow(lstRow);
}

JTable table = new JTable(model);
// Kleopatra is so going to kill me for this :(
Dimension size = table.getPreferredScrollableViewportSize();
size.height = table.getRowCount() * table.getRowHeight();
table.setPreferredScrollableViewportSize(size);

JOptionPane.showMessageDialog(null, new JScrollPane(table));

public static class MyModel extends AbstractTableModel {

    public static final String[] DAY_NAMES = {"S", "M", "Tu", "W", "Th", "F", "S"};
    private List<List<String>> lstRowValues;

    public MyModel() {
        lstRowValues = new ArrayList<List<String>>(25);
    }

    @Override
    public int getRowCount() {
        return lstRowValues.size();
    }

    @Override
    public String getColumnName(int column) {
        return DAY_NAMES[column];
    }

    @Override
    public int getColumnCount() {
        return 7;
    }

    @Override
    public Object getValueAt(int rowIndex, int columnIndex) {
        List<String> rowData = lstRowValues.get(rowIndex);
        return rowData.get(columnIndex);
    }

    public void addRow(List<String> lstValues) {
        lstRowValues.add(lstValues);

        fireTableRowsInserted(getRowCount(), getRowCount());
    }
}

    Or you can go have a look at JXMonthView

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