import java.util.*;

public class Demo
{
    public static void main(String[] args )
    {
        
        GregorianCalendar d=new GregorianCalendar();
        
        int today=d.get(Calendar.DAY_OF_MONTH);
        
        int month=d.get(Calendar.MONTH);
        
        d.set(Calendar.DAY_OF_MONTH,1);
        
        int weekday=d.get(Calendar.DAY_OF_MONTH);
        
        System.out.println("Sun Mon Tue Wed Thu Fri Sat");
        
        for(int i=Calendar.SUNDAY;i<weekday;i++)
        
        System.out.print("    ");
        
        do
        {
            
            int day=d.get(Calendar.DAY_OF_MONTH);
            
            System.out.printf("%3d",day);
            
            if(day==today)
            
            System.out.print("*");
            
            else
            
            System.out.print(" ");
            
            if(weekday==Calendar.SATURDAY)
            
            System.out.println();
            
            d.add(Calendar.DAY_OF_MONTH,1);
            
            weekday=d.get(Calendar.DAY_OF_MONTH);
            
        }
        while(d.get(Calendar.MONTH)==month);
        
        if(weekday!=Calendar.SUNDAY)
        
        System.out.println();
        
    }
}
不知道问题出在哪里，请帮帮忙！

程序可以运行，你指的是输出格式有问题吧

do｛｝里面最后一句改成：weekday=d.get(Calendar.DAY_OF_WEEK);
看看是不是你想要的结果！

if(day==today)改为equals 判断试试

import java.util.*;

public class Demo
{
    public static void main(String[] args )
    {
        
        GregorianCalendar d=new GregorianCalendar();
        
        int today=d.get(Calendar.DAY_OF_MONTH);
        
        int month=d.get(Calendar.MONTH);
        
        d.set(Calendar.DAY_OF_MONTH,1);
        
        int weekday=d.get(Calendar.DAY_OF_WEEK);
        
        System.out.println("Sun\tMon\tTue\tWed\tThu\tFri\tSat");
        
        for(int i=Calendar.SUNDAY;i<weekday;i++)
        
        System.out.print("\t");
        
        do
        {
            
            int day=d.get(Calendar.DAY_OF_MONTH);
            
            System.out.printf("%3d",day);
            
            if(day==today)
            
            System.out.print("*\t");
            
            else
            
            System.out.print("\t");
            
            if(weekday==Calendar.SATURDAY)
            
            System.out.println();
            
            d.add(Calendar.DAY_OF_MONTH,1);
            
            weekday=d.get(Calendar.DAY_OF_WEEK);
            
        }
        while(d.get(Calendar.MONTH)==month);
        if(weekday!=Calendar.SUNDAY)
        
        System.out.println();
        
        
    }
}

更改过的。你看看。qq截图是运行后的效果图。