请教关于万年历的事情

package 万年历;

import java.util.Scanner;

public class calendar {
   


    public static void main(String[] args) {
        int year,month,day=1,j,i;
        int[][] a;
        a=new int[5][7];
        @SuppressWarnings("resource")
        Scanner cin= new Scanner(System.in);
        year=cin.nextInt();
        month=cin.nextInt();
        if((year%4==0&&year%100!=0)||year%100==0)
            if(month==2)
            {
                for(i=0;i<5;i++)
                {
                    for(j=0;j<7;j++)
                        a[i][j]=day;
                        System.out.print(a[i][j]+"\t");
                        day++;
                        if(day>=28)
                        {
                            break;
                        }
                }
                System.out.println();
            }
    else
    {
        if(month==2)
        {
            for(i=0;i<5;i++)
                {
                    for(j=0;j<7;j++)
                    {
                        a[i][j]=day;
                        System.out.print(a[i][j]+"\t");
                        day++;
                        if(day>=29)
                        {
                            break;
                        }
                    }
                    System.out.println();
                }
            }
        }
        if(month==1||month==3||month==5||month==7||month==8||month==10||month==12)
        {
            for(i=0;i<5;i++)
                {
                    for(j=0;j<7;j++)
                    {
                        a[i][j]=day;
                        System.out.print(a[i][j]+"\t");
                        day++;
                        if(day>31)
                        {
                            break;
                        }
                    }
                    System.out.println();
                }
        }
        else if(month==4||month==6||month==9||month==11)
        {
            for(i=0;i<5;i++)
            {
                    for(j=0;j<7;j++)
                    {
                        a[i][j]=day;
                        System.out.print(a[i][j]+"\t");
                        day++;
                        if(day>30)
                        {
                            break;
                        }
                    }
                    System.out.println();
            }
        }
    }
}
            
        
        
        // TODO 自动生成的方法存根

   
这是我的程序，可是我不会把每月第一天放在星期几，应该怎么改进这个程序才会像正常的日历一样
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可是我不会把每月第一天放在星期几
这句话什么意思？
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