GridLayout .add错误

Question

我的程序中似乎有一个错误，我无法解决我的生活问题。

以下是代码：

import javax.swing.*;
import javax.swing.text.*;

import java.awt.*;
import java.util.*;

public class CalendarGUI extends JPanel {
    ProgramCalendar currentCalendar;
    GregorianCalendar sideCalendar; 
    String[] month = {"January", "February", "March",  "April", "May", "June", "July", "August",
            "September", "October", "November", "December"};

    public CalendarGUI(ProgramCalendar pc){
        currentCalendar = pc;
        sideCalendar = new GregorianCalendar();
        JPanel calendarSidePanel = new JPanel();
        calendarSidePanel.setSize(400,400);
        calendarSidePanel.setLayout(new BorderLayout());
        //sets month
        JTextPane monthText = new JTextPane();
        monthText.setText(month[sideCalendar.get(Calendar.MONTH)]);
        calendarSidePanel.add(monthText, BorderLayout.NORTH);

        //main part of error
        JPanel sideCalendarMain = new JPanel(new GridLayout(6, 7, 5, 5));

        JTextPane sun = new JTextPane();
        sun.setText("Sun");
        sideCalendarMain.add(sun);

        JTextPane mon = new JTextPane();
        mon.setText("Mon");
        sideCalendarMain.add(mon);

        JTextPane tues = new JTextPane();
        tues.setText("Tues");
        sideCalendarMain.add(tues);

        JTextPane wed = new JTextPane();
        wed.setText("Wed");
        sideCalendarMain.add(wed);

        JTextPane thurs = new JTextPane();
        thurs.setText("Thur");
        sideCalendarMain.add(thurs);

        JTextPane fri = new JTextPane();
        fri.setText("Fri");
        sideCalendarMain.add(fri);

        JTextPane sat = new JTextPane();
        sat.setText("Sat");
        sideCalendarMain.add(sat);

        calendarSidePanel.add(sideCalendarMain, BorderLayout.CENTER);

        add(calendarSidePanel);
        setSize(1000,1000);
    }

}

问题在于我认为它会显示为：

            April
Sun Mon Tues Wed Thurs Fri Sat

而不是

 April
Sun Mon
Tues Wed
Thurs Fri
Sat

目前正在显示。

我是否只是在滥用GridLayout，或者是否存在其他一些我遗漏的基本错误，或者是一些随机错误。 感谢